Essays

One of the most-read and commented upon essays I’ve ever written is this paper on Diego Rivera and fresco painting. I wrote it for a class I took from a chemist entitled, “Chemistry in Art.” This was a class about how a chemist looks at art, and was eye-opening and fascinating. I had always wondered about the physicality of frescoes, so I researched and wrote this paper.

Fresco Painting and the U.S. Frescos of Diego Rivera

Kent L. Boyer

Introduction to the Paper

The intent of this research paper is to explore the chemistry of and technique used in the time-honored art medium of fresco painting.  The second section of the painting reviews Diego Rivera’s fresco technique in the context of his fresco work in the United States in the decade 1930 – 1940.

It’s been said that the “ancient art of fresco turned an unknown Diego Rivera into ‘the world’s greatest muralist.’” (Hurlburt 99) Fresco is, of course, not really mural painting; rather it is an ancient Mexican and European form of wall painting that involves applying water-based pigment to fresh plaster. (Indych-Lopez 78)

The first section of the paper explains the history of fresco as an art form, a glossary of the terms used in fresco, the chemistry of fresco, preparation of the substrate, how to transfer the fresco drawings onto the wall, fresco palette and pigments, and finally some of the common hazards and deleterious effects to which frescos are susceptible.

In the second section, the paper looks at Diego Rivera’s fresco work – focusing on his work in the United States between 1930 and 1940.  The paper investigates anecdotes about Diego Rivera’s adherence to traditional technique, his palette, and a review of his major U.S. fresco work.  We also look into his innovative moveable fresco.

Section 1: Chemistry in the Art of Fresco Painting

Section 1.1: Fresco Painting Overview and Terminology

The word fresco means “fresh” in Italian.  There are two kinds of fresco painting: “buon” fresco (true) and “secco” fresco (false). (Hurlburt 253)  Buon painting is done directly on freshly laid wet plaster using pigments dissolved in limewater.  As plaster and pigment dry together a chemical reaction causes them to become completely integrated.  As the wet plaster – calcium hydrate – reacts with naturally occurring carbon dioxide from the atmosphere, the wall and paint together become calcium carbonate.   Fresco paintings have been relying on this chemical reaction for a thousand years.

Secco fresco, on the other hand, is the less permanent technique of applying colors over a dry undercoat – using colors that are not lime-resistant.  Some fresco artists use this technique to put finishing touches on their buon fresco.  Secco fresco is usually painted with tempera paint mixed with gum arabic, casein, animal skin glue, or acrylic binders. (Fresco Techniques)

Buon fresco is a difficult painting technique for many reasons. Fresco painters usually work very large – often larger than life-size.  Their drawing perspective and figure foreshortening techniques must be spot on to satisfy the eye of the viewer on the floor who is looking up at the work.  The artist must hire and supervise a team of assistants – s/he cannot do all the work alone.  S/he will spend much of her/his time climbing ladders and scaffolding and working in odd positions and at dizzying heights for long hours at a time. 

Finally and most important, the days’ painting must be accomplished in its entirety when the plaster is damp.  This means that the painting (or the section the artist wants to finish today) must be completed “live” – in real-time.  S/he cannot hesitate, rethink an idea, or return to that section to make corrections.  While temperature and humidity affect the plasters “open window,” the artist usually has between 6 and 18 hours to complete the day’s work. If a mistake is made that requires correction, the plaster must be chiseled away to begin the process again. (Ruskin and West 4) 

Despite the troublesome regimen of buon fresco, painters from ancient times forward have chosen it to decorate walls – for primarily one reason.  It is the most durable of all wall painting mediums.  Why?  Because the artist’s paint doesn’t lie on the surface of the wall, it actually becomes the wall with a chemical reaction.  And once the fresco is dry, it cannot be washed, peeled, or worn away – it is impervious to practically everything. (4)

Since the chemical reaction that occurs is between the fresh plaster and the pigments, not any pigments will do.  The pigments used in fresco must be able to withstand the alkaline calcium hydroxide in the plaster and in the “lime water” the pigments are mixed with.  The lime itself is technically the binder in fresco paint – in a similar way that linseed oil is the binder in oil paint. (Hurlburt 253)  The paint itself actually only slightly penetrates the fresh plaster wall before it becomes permanently bonded with the wall.  This bond is due both to naturally occurring CO₂ in the air and to evaporation.  Baglioni, in his paper on autogenous lime grouts, describes this process by writing, “… the pigment remains petrified on the surface.”

He goes on to write,

The setting process of lime-based mortars occurs through drying and carbonatation. During drying, excess water in the mortar evaporates and the plaster contracts. The process of carbonatation, responsible for the binding of the pigments, occurs according to the following equation: 

Ca(OH)₂ + CO₂ -> CaCO₃ + H₂0

In the fresco technique, calcium carbonate, formed by the reaction of calcium hydroxide with carbon dioxide from the atmosphere, traps and fixes the pigments on the surface. (43)

Once it is dry, fresco is impervious to moisture and therefore must be chipped away, replastered, and repainted if a mistake is made. The water-based pigment binds to the plaster as it dries, leaving the wall a chemically inert and moisture-proof surface.  (Ruskin and West 4)

Section 1.2: Fresco Substrate Preparation

Fresco painting technique begins with fastidious preparation of the wall that is to receive the painting.  If it is an old wall, it should be carefully examined for evidence of water absorption through the wall from the outside.  This would appear as dark or moist stains on the wall.  The wall must also be examined carefully for a salty efflorescence – often a sign of the presence of potassium nitrate (KNO₃ or saltpeter).  Efflorescence of this nature will prevent the curing of the fresh plaster and paint because it interferes with the chemical bond. As a result the fresco may be discolored or may not adhere properly to the wall.  There are no second chances with buon fresco, so if the wall isn’t properly prepared the plaster in that area will have to be chiseled away and the painting done again. (Hale and O’Sheel 13)

Laurance Hurlburt, author of The Mexican Muralists in the United States, wrote that a new plaster wall should set for a year an artist attempts to paint a fresco on it.  When getting ready to paint a fresco, artists often require all the old plaster to be removed and the wall to be replastered.  However, if this is not done, the existing wall should at least be hosed down daily for a week in order to obtain a firm bond between the old plaster and the new.  The goal of this repeated washing is to remove any potassium nitrate that may be present on the surface. (253) Nordmark, in Fresco Painting: Modern Methods, recommends three washings to prepare an old wall – first with a weak solution of hydrochloric acid (HCl), followed by hot water, and then cold water.  The wall should thoroughly dry in between washings. (3)

The traditional fresco plaster recipe uses a mixture of slaked lime, sand, and/or marble dust mixed with water to create the fresco substrate.  Slaked lime is a product that results from mixing caustic lime and water and allowing it to age – sometimes for years – to create the so-called “lime putty” that binds the pigment to the plaster. (Hurlburt 254-255) 

The preparation of slaked lime is a time-consuming one.  The first step is written this way:

CaCO₃ (s) + HEAT -> CaO (s) + CO₂ (g)

Limestone (CaCO₃) is calcined (heated) at 800 – 900 degrees Celsius to make porous lime – CaO (calcium oxide).  Author Nordmark calls the raw ingredient “high calcium lime” and note that high calcium lime is what bones are composed of.  (9)

Next, the lime is slaked – this process adds 2 or 3 molecules of H₂O per each molecule of lime and yields a product called calcium paste or lime putty. 

(CaO(s) + H₂0(l) -> Ca(OH)₂(s) + HEAT

Lime putty is an aqueous gel of thin crystals of calcium hydroxide.  The lime putty is mixed with the sand or marble dust to create the plaster.

Historically, lime was slaked in pits, troughs, or barrels for a number of months to several years to obtain lime putty of the right consistency. (Hale and O’Sheel 16)  Michelangelo used plaster aged for up to ten years. (Nordmark 16) The Kremer Pigments Company, a modern manufacturer and supplier of historically-correct artist supplies uses a wood-burnt slaked lime pit to prepare its slaked lime product  – and boasts that it’s made from 98% pure calcium carbonate limestone and slaked a minimum of 5 years. (Kremer Pigments)

Fresco plaster is made by combining the slaked lime with varying portions of sand or marble dust.  Many artists use a recipe that has a decreasing proportion of sand on successive plaster layers providing the artist a smoother surface on which to paint.

The sand used in the plaster mixture must be completely free of organic impurities like sea-salt, clay, and mica. (Hurlburt 256)  Angular particles are better than round – washed river sand is best because it has the angular shape for proper interlocking.  (Fresco Techniques)  Fresco Painting author Gardner Hale writes that brown sand is better than white sand for two reasons.  Using bright white sand for fresco plaster results in an “unpleasant cold tint” to the painting.  Further, white sand usually comes from beaches where it is contaminated with salt – the natural enemy of fresco. (17)

The lime putty (slaked lime) and sand are mixed with as little distilled water as possible to produce the strongest binding quality to the plaster.  In some plaster recipes animal or vegetable fibers soaked in lime putty are added to strengthen the first layers of plaster.  The plaster is applied to the wall in several coats to decrease the possibility of cracking which would damage the painting. (Hurlburt 253-259)

Traditionally the first coat laid down is called the roughcoat, scratchcoat, or, in Italian, “trullisatio.”  Course sand can be used in the scratchcoat, but finer sand is better for the next coats. The roughcoat is scratched with a comb-like tooth edged trowel tool to increase the grip of the next coat.  The artist assistant working as the plasterer throws the roughcoat by trowel on a water-saturated wall.  The roughcoat layer should be approximately ½ inch thick. (259) The wall must dry for days in between each plaster coat.

Some artists add a coat called the floatcoat.  Particularly if cement has been added to the roughcoat for strength (a common modern practice), a floatcoat provides for a smooth plaster base for the next coat. If used, this coat is finely leveled and floated with a tool called a darby. (Fresco Techniques)

The next coat to be applied to the wall is called the browncoat or “arriciato.”  The browncoat uses less sand than the roughcoat. (Nordmark 28) It should be about 1/3 inch thick and is usually mixed up using less water than the roughcoat.  

Finally, the plaster coat that will be painted upon is added – this is the finish or  “intonaco” coat.  The intonaco coat is only applied to the wall in that section the artist can complete painting during that day – within 6 to 18 hours.  This coat is smoothed and burnished (called “floating”) to the desired texture with a wooden or metal float as it begins to set. The wall is then prepared for the artist to take up her/his palette.

Some traditional fresco recipes use a sand to lime ratio of 2:1. Other recipes recommend a ratio of 8 parts sand to 5 parts lime.  Whichever recipe one follows, it’s important to keep the same proportion for the entire wall. (Hurlburt 254-259; Hale and O’Sheel 17; Fresco Techniques)

It’s easy to see why an extensive error would result in a great deal of work to correct it.  The plaster – all the way down to the roughcoat – would have to be chiseled out and the wall layering and preparation process begun again.

As the painting begins, the fresco artist must decide what each next day’s work will include – only that portion of the wall will have the intonaco layer applied by the plasterer for the next day.  Because the fresco painting must be begun and finished in the same work session, once the intonaco layer is applied the artist must complete that portion of the painting while the layer is damp.  It is critical to the finished work that the artist’s assistants mixing the paint match the colors perfectly to the previous days’ work– a task complicated by the fact that fresco color fades as the chemical reaction of hardening occurs.  In addition, the artist must perfectly match composition and style so the finished wall appears as one cohesive work even though it’s been painted over weeks or months. (Hurlburt 254)

The amount of painting an artist plans to do each day is called the “giornata.”  In buon fresco, the artist must carefully decide where the cutline or the leading edge of that day’s work should be located. (Fresco Techniques) To lessen the visibility of the cutline in the finished work, it should be curved to mimic a composition line in the fresco – although it’s wise to keep it a simple curve.  In addition, the cutline should be planned for a dark passage in the image to further mask it from the viewer. (Hale and O’Sheel 29)

The plasterer is one of the important artist’s assistants on a project and often functions as the chief assistant.  In historic times, the plasterer was often a student or apprentice artist.  In modern times, the plasterer may be a fellow fresco artist between jobs or an artist perhaps not yet as well known as the artist on the commission.

A fresco painting team is like a small factory.  They work in shifts on a sort of art assembly line for the entirety of the project – sometimes virtually 24 hours a day.  The artist often has the plasterer start to prepare the wall early in the morning – perhaps as early as 6 am.  Other artists have their plasterer work during the night so the wall is ready for paining in the morning. The plasterer’s wall preparation includes these steps:

1. The plasterer begins by thoroughly wetting the wall from the bottom up.
2. S/he marks the area to be plastered, following the artist’s instructions from the day before.
3. The plasterer mixes the plaster using the lime putty and sand or marble.  The specifications of the layer are the same for the entire project.  
4. S/he lays the skimcoat and floats it using special tools.
5. The skimcoat is allowed to begin to set up for 15 or 20 minutes, until it’s just hard enough to take a slight pressure of the finger.
6. The intonaco coat putty is readied and applied to the wall.  It should have the consistency of butter.
7. The artist now has between 6 and 18 hours to paint – the open time being a factor of temperature and humidity. (Nordmark 39, 49-59; Hale and O’Sheel 19)

Section 1.3: Transferring the Drawing onto the Substrate

Over time, fresco artists have used a number of techniques to get their drawings onto the walls in order to paint in fresco.  Before Giotto’s time, fresco artists drew directly on the browncoat layer using a wash of sinopia to create an underdrawing.  Sinopia is a reddish, greenish, or brownish earth color.  It means “red earth” and was an iron oxide pigment historically from Sinopia in present day Turkey.  The source of the mineral pigment has long ago been depleted but the wash is often still referred to as sinopia. (Fresco Techniques)

Because the browncoat must be covered with the final coats of plaster before the artist can paint, the drawing had to be obliterated for each day’s work and then quickly resketched on the intonaco coat.  

About the middle of the 15^th century, artists began to use paper cartoons to transfer their art to the walls.  A cartoon is an actual-size drawing prepared for each section of the wall on draftsman paper.  Giotto was the first artist to utilize paper cartoons for fresco. (Nordmark 16; Fresco Techniques)

How the full size drawing – the cartoon – comes into being is a matter of artist preference.  Some fresco artists sketch intricate scaled drawings that are then enlarged by assistants to full-scale paper cartoons.  Other fresco artists draw on large rolls of paper with the dimensions of the wall marked on them.   Still others paint a loose drawing onto the browncoat itself.  Their assistants trace the drawings using translucent paper, thus creating the cartoon.

Once the intonaco layer of plaster is applied, the wall is again a blank white slate. The cartoon drawing must now somehow be transferred to the wall.  The time- honored technique (there are variations) is for the cartoon to be pinned to the intonaco layer and the drawing transferred to the wall in the following manner:

1. First, an assistant using a spiked wheel tool or a large sewing needle traces the cartoon lines, thus creating a dotted perforation line on the cartoon paper.

2. Next, the assistants, who have made small pouches or bags of muslin or cheesecloth and fill them with powdered pigment – charcoal black, light red, or terra verde pigment, use them to transfer the drawing.

3.  The porous bag of pigment is pounded lightly at the perforation lines on the cartoon, which transfers the drawing to the soft intonaco layer. The term used for this is process is pouncing. (Ruskin and West 4; Nordmark 44; Hale and O’Sheel 28)

The paper cartoon is then removed from the wall. At this point, an assistant may “connect the dots” by painting a loose line over the drawing, or the artist may prefer to do this her/himself.  This line is painted with a light red or brown pigment mixed with limewater on the intonaco layer.

All of this work can happen each morning (or during the night) before the artist even gets to the site.  After hours and hours of preparatory work, the wall is finally ready for the artist to paint.

Once the artist has finished for the day, assistants again go to work preparing for the next day’s painting.  Often, scaffolding must be moved or readied, cartoons must be readied for the area the artist has indicated s/he will paint the next day. Pigments must be mixed and the plasterer must rise early to prepare the wall.  Fresco painting is very nearly a 24-hour a day enterprise.

Section 1.4: Fresco Palette and Pigments

Because of the alkaline nature of the plaster, fresco artists have been using the same pigments (with a few exceptions) for centuries.  Fresco pigments are generally earth minerals  – that is, they come from the soil.  The colors must resist the alkalinity of the lime. (Hale and O’Sheel 20)

The pigments must be tested for permanency against not only the alkalinity, but also for permanency against the effects of light, hydrogen sulfide and ammonium hydroxide.  They must also be pure and free of organic contaminants. (Hurlburt 254; Fresco Techniques)

Another assistant artist on the team is the person who prepares the pigments.

The pigments are ground very finely in distilled water to ready them for use.  Alcohol may be added for those pigments that are difficult to grind in water.  Distilled water is utilized in pigment grinding to avoid mold or other contaminants. (Nordmark 62)

The process of grinding pigments is a lost art.  Hale writes (in 1933) that grinding pigments familiarizes the artist with each color’s habit or characteristics.  “Some are thin and transparent, others are fat and opaque,” he writes.  “Some require little water, others a surprising amount.” (23)

Grinding pigments requires a glass or marble slab on which to grind and a special tool called a muller used to do the grinding.  The muller is usually made from glass and resembles a pear with the bottom cut flat.  Alternately, a traditional mortar and pestle can be used. (Nordmark 61)

The assistant prepares two panels once the pigments are ground – one panel mixed with plaster for pigment testing and the other panel a color chart.  Pigments applied to the moist intonaco layer dry much lighter than when they are painted.  The color chart helps the artist gauge the intensity difference while painting, so that each day’s work matches the previous day. 

Dried ground colors are scooped up and put in a storage jar.  Wet storage of color (say from day to day) is more difficult – the liquid pigment must be stored in Mason-type canning jars with glass lids, not metal.  The jars, lids, and seals must all be boiled just as when canning fruits or vegetables. (59) This ensures that the fresco pigment stays free of mold and other contaminants.  Most fresco artists prefer to use fresh colors every day.

To mix the paint for the days’ painting, lime putty thinned with distilled water is mixed with the ground pigments to create a thin paint.  The thinned lime putty is called milk of lime. (Fresco Techniques)

Viewers of frescos are often surprised to learn that most fresco artists’ palettes contain no more than twelve to fourteen colors.  The common pigments are:

1. Reds – cadmium red (deep and brilliant), light red (English red), Venetian red, caput mortem (light and dark), terra rosa, terra de Treviso, terra Pozzuoli
2. Oranges – cadmium orange
3. Yellows – cadmium yellow (medium and deep), yellow ochre, golden ochre, dark ochre, Mars yellow, Naples yellow (light and dark)
4. Greens – vert emeraude, oxide of chromium opaque, green earth, Veronese green earth
5. Blues – cobalt blue, deep cerulean blue, ultramarine blue
6. Violets – Mars violet, ultramarine violet
7. Blacks – ivory black, vine black, charcoal black
8. Browns – brown ochre, burnt sienna deep, burnt umber greenish, burnt umber, burnt green earth (Nordmark 52-53)

Practitioners of strict buon fresco technique don’t use white pigment – instead they use the white of the plaster wall to create areas of white or highlights in their painting. Hale writes,  “…the beauty of the medium depends on the white of the plaster illuminating the semi-transparent pigment, as does the light in a fine old stained glass which time has made half-opaque.” (29)

In my research for this paper, I came across a fascinating story about a chemist, Dr. George Kremer. His research into historical artist pigments lead him to start international company supplying restorers and conservators with historically-correct artist supplies. Kremer began this turn of his career by undertaking to recreate a blue pigment from antiquity called smalt blue.  This pigment was originally developed in 2000 BC.

Kremer has now matched over 80 historical (pre-1704) artists’ pigments – among them fresco pigments.  It’s been said that the ingredient list for Kremer Pigments reads like an alchemal textbook.  Here are some of the more interesting ones:

• vermillion (made from cinnabar gathered in a remote Chinese province)
• condensed cattle urine
• dried lice
• madder root
• arsenic sulphur
• lapis lazuli
• malachite
• Lean Tin Yellow
• South American Maya Blue
• Egyptian Blue

Kremer Pigments makes and sells the very same sepia pigment used by Leonardo.  It’s made from the ink of the Adriatic cuttlefish. Kremer’s most expensive pigment is a shade of magenta.  1 gram of the pigment is made of secretions of 8000 magenta snails (murex trunculus) from New Zealand.  It sells for $392 per gram.  For comparison, the Lapis Lazuli blue Fra Angelica used is $37.50 per gram.

Kremer’s customers include international conservators and restorers who have said the pigments have a “heavenly luminosity,” “unmatched brilliance,” and “transcendental character.” (Kremer Pigments)

The Kremer Pigments website includes their recipe for fresco pigments.  They recommend that to every 1.7 parts of distilled water, 2.3 parts limewater should be added.  Next the lime-proof pigment is added in a sufficient quantity to color the wash.  Fresco paints are mixed to a wet consistency – runnier than other paint mediums – and they tend to splash.  Kremer’s website includes a note to artists to be careful as lime is caustic when wet and burns skin.

Finally, this list of Kremer’s Lime Fresco Pigments is found on the company website:

• Sugar Dolomite
• Red Jasper
• Rhodochrosite
• Cote D’Azur Violet
• Florentine Green
• Andeer Green
• Green Jasper
• Green Quartz
• Celadonite
• Nero Bermino
• Alba Albula
• Smalt Blue
• Egyptian Blue
• Egyptian Green
• Ploss Blue
• Sodalite
• Vesuvianite
• Lapis Lazuli
• Ultramarine Ash
• Pyrite Powder
• Verona Green Earth
• Bavarian Green Earth
• Russian Green Earth
• Aegirine
• Epidote 

The history of the development of the traditional buon fresco technique is full of interesting experiments.  Leonardo, who painted many walls,  often experimented  with various substances.  To some of his wall paintings, he may have applied a thin layer of colorless “Greek pitch,” a resin and wax substance used at the time to waterproof the hulls of boats. In other experiments, Leonardo may have mixed this Greek pitch with gesso and linseed oil to prepare a wall for oil painting. (Farago 313)

Farago’s paper on “Leonardo’s Battle of Anghiari” relates that in 1527 that Leonardo combined walnut oil with colors on plaster.  The result was unsuccessful. Later, around 1540, Farago writes that Leonardo tried to revive an ancient experimental method of “coloring stucco” with an encaustic recipe.  (311)

Leonardo’s Last Supper (1495-1498) shows wide variation of media from one part of the surface to another.  It is known that Leonardo experimented with oil media directly on the Last Supper surface.  Whether because of his experimentation with media and/or the chronic moistness of the wall wicked in from the external atmosphere (or both), the Last Supper has been deteriorating since the time it was painted.  (312)

A transection of the Last Supper wall reveals fresco plaster, but also a white ground of another substance and a layer of lead white oil paint.  (314)  Leonardo wasn’t the only early fresco artist to experiment with various products and techniques. Many fresco artists have tried to improve upon and/or shortcut the buon fresco technique over the centuries.

Section 1.5: Applying the Paint to the Wall

The wall has been prepared, the cartoons pounced, and the pigments mixed – the fresco team is now ready for the artist to paint.  Brushes used for fresco painting must be very soft to avoid marring the soft, tender intonaco layer.  The artist must also employ the lightest of touch for the same reason.  Palettes used are typically cheap white china or enamel plates, since lime colors adhere permanently to the palette.  The plates used are discarded at the end of each daily session. (Nordmark 64-65)

In traditional buon fresco technique, the artist uses a mixture of Mars black and yellow ochre called “verdaccio” to create a monochromatic underpainting for tonal values before the transparent color layers are added.  Fresco painting technique involves superimposition of one color over another – building layers rather than mixing. This technique has been known for centuries – studies of Michelangelo’s Sistine Chapel paint composition reveal that he used yellow over black to make green and red over yellow for a vivid orange. (Bell 93; Fresco Techniques)

The artist has between 6 and 18 hours after the intonaco layer is applied to the wall to complete the day’s work. The artist must rely on her/his experience and the color chart prepared by the assistant to paint deeper and more intense color knowing that the pigments become lighter as they dry. (Hurlburt 254)

Section 1.6: Curing

In essence, fresco colors do not penetrate the plaster – they become the plaster, when in the process of drying the lime is carbonized and at length recovers its original properties as calcium carbonate or limestone. (Helm 43)

The fresco-curing steps are both chemical and physical processes that occur simultaneously.  The steps are comprised of three elements:

• the absorption of water into the wall
• the evaporation of water from the surface of the wall, and
• carbonation of the slaked lime by carbon dioxide in the atmosphere, represented by this equation:

Ca(OH)₂(s) + CO₂(g) -> CaCO₃(s) +H₂0

Once it is dry, the fresco is impervious to moisture and therefore must be chipped away, replastered, and repainted if a mistake is made which requires repainting. (Ruskin and West 4) The water-based pigment binds to the plaster as it dries, leaving the wall a chemically inert and moisture-proof surface. 

Section 1.7: Common Enemies of Fresco

Fresco paintings have a significant lifespan.  In his book Fresco Painting, Gardner Hale says that outdoors, fresco has probably one hundred good years and perhaps two or three hundred additional years of “faded charm.”  Indoors, fresco potentially has a longer lifespan, but that depends greatly on the artist’s original technique and the conditions of humidity, light, and air quality in the room. (5)

Hale writes that indoor fresco, “… given proper protection… can easily see a thousand years.” He goes on to warn, however, that fresco, once cured, is actually the wall itself and as such, is subject to “… faulty construction and crumbling and destruction of material to dampness and the germ it breeds – saltpetre (sic). (4-5)

The capillary action of an improperly sealed exterior wall or a high water table leading to chronic dampness and the formation of salts are the main enemy of fresco.  These salts sometimes show up as a whitish exudation called efflorescence, a powdery substance or incrustation that flowers or blossoms from the wall. (Nordmark 3; Fresco Techniques)

In addition to damage caused by dampness and salts, there are the inherent consequences of potential delamination due to the stratigraphic nature of wall paintings.  “Variations in temperature, relative humidity, and other factors produce mechanical and physical stresses that can be responsible for the … detachment of these layers.” (Baglioni 43)

The solution for these types of problems is to consolidate the layers again by introducing a binding agent using a syringe to readhere the detaching layers.

In a study looking for the best materials to inject into delaminated frescos, Baglioni notes that “…the problem of absence of air, in particular CO₂, when grouting with lime-based grouts can be solved by the addition of CO₂-producing compounds. These so-called autogenic grouts are lime-based grouts that can be used instead of hydraulic grouts. There are good reasons to avoid hydraulic grouts, bearing in mind the possibility that they may release soluble salts that are known to be one of the most serious causes of deterioration in wall paintings.” That is to say that injecting a lime-based grout to re-adhere a portion of the fresco seems intuitive, but the lack of CO₂ in the “bubble” makes the desirable chemical curing impossible unless CO₂-producing compounds are components of the grout. (43, 50)

The study goes on to show that esters of carbonic acid (such as carbamates or urethanes) can be used to prepare this so-called autogenous lime-based grouting mixture.  The study shows that grouting with this composition is successful even in areas with very low concentrations of CO₂. (50)

In general, once frescos are finished, they should be left alone.  They shouldn’t require even cleaning for many decades.  Nordmark suggests allowing at least two decades to go by before even considering vacuuming a fresco.  And then, he says, never use a brush that could scratch the surface.  The best technique is to use the broad nozzle of a vacuum against a linen screen so the vacuum itself never actually touches the wall. 

Nordstrom goes on to explain that if an area becomes soiled with soot or loose dirt, neither art gum or rubber erasers should be used, as they both leave a sulphur film that’s dangerous to certain colors.  Instead, he recommends an ancient technique using soft bits of bread to “erase” the dirty area. (102-104)

Section 2: The U.S. Frescos of Diego Rivera

Section 2:1 Diego Rivera and Fresco

At age 21, Diego Rivera left the Mexican art school he had been attending and moved to Europe to study art – not an uncommon practice at the time for serious North American art students. He lived first in Madrid, then moved to Paris where he became friends with Modigliani, who famously painted his portrait.  He also developed a lifelong friendly competition with Picasso and Braque, who were working in the Cubist style at the time he met them.  After 2 years in Madrid and 11 in Paris, in 1920 he moved to Italy for a year.  Here he found his medium – in his study of the masters, he fell in love with 13^th century painter Giotto’s frescos. (Evans 30)  He was drawn to fresco as a sister decorative art to architecture and sculpture – the collaboration of the three disciplines.

In addition to his interest in fresco as an important decorative art, fresco also offered another attractive characteristic for Rivera.  An outspoken and devoted Marxist, socialist, and sometime Communist (he was expelled by the Mexican Communist party in the 1920s but reinstated a few years before his death), Rivera was committed to public art as an anti-bourgeois statement.  He believed that art should be accessible to the masses rather than being purchased like a commodity by rich patrons and then hidden out of site in their homes. Fresco was the perfect art form to express this ideal- when painted on the walls of public buildings, it was the ultimately accessible painting form.

When Diego returned home from Italy in 1921, he found that essentially no one in Mexico was working in buon fresco.  He began to successfully solicit commissions and build his reputation as a master of fresco.  

In 1922, at the age of 36, Rivera painted his first wall painting – an encaustic painting called Creation at the National Preparatory School in Mexico City.  Trying to improve upon his imperfect knowledge of historical techniques, he thought encaustic would be more durable than painting with water-based pigments.  He incised his drawing deep into the plaster so the outlines would be imperishable and then applied the melted wax color.  However, he found that encaustic was a difficult technique for large wall paintings and never worked in it again. (Kettenman 24; Rochfort 35-36)

Rivera had two contemporaries in Mexico who were also interested in the fresco medium – Orozco and Siquiera.  All three of the young artists were interested in fresco as “the synthesis of architecture, painting and sculpture.” (Rochfort 165)  All three did fresco work both in Mexico and the United States.  

However, neither Orozco nor Siquiera respected the historical technique of buon fresco like Rivera did.  Siquiera, the youngest of the three artists, was an innovator who experimented with automobile paint and other media – with varying permanence results.  Orozco, an interesting man with a sharper, more intense personality than Rivera, invented shortcuts and often used a combination of buon and secco fresco in his work.

The three artists discovered a book of Italian fresco recipes written by Cellini (a contemporary of Michelangelo) and had it translated from Italian, but after translation the antique ingredient names were unknown to the Mexican painters. (Rochfort 35)

Rivera’s first buon fresco technique was developed by an assistant whose father had learned it in trips to pre-Columbian Teotihuacan.  The technique was similar to techniques employed in the ancient Toltec society to paint on walls.  Besides being less difficult than his encaustic mural (which, by the way, still exists and is beautiful), the new technique also appealed to Rivera on the merits of his life-long interest in nationalism for his homeland.  Mexican press, also fiercely nationalistic, reported “Diego Rivera Discovers Secret of Ancient Mexico.” (Rochfort 165)

In 1922, Rivera received the commission that would launch his pre-eminence as the world’s greatest fresco painter.  He was hired to decorate the Secretariat of Public Education building in Mexico City with 124 fresco paintings depicting Mexican history and society.  The walls were finished in 1928.  During the painting of these frescos, Rivera spoke often about what he called “The Trinity” – the collaboration of the painter, the sculptor, and the architect in the creation of public art spaces. (Evans 30) Rivera experimented during this time period with an ancient Meso-American technique using nopal cactus liquid in his paints.  (Kettenmann 26) Ultimately, though, Rivera’s fresco technique reverted to the precise and time-honored practices of the artists of Renaissance Italy.

Some of Rivera’s best known Mexican murals from this period are featured at the National School of Agriculture in Chapingo, (1925–27), in the Cortés Palace in Cuernavaca (1929–30), and the National Palace in Mexico City (1929–30, 1935).   

Rivera had two children in the early 1920s from a first marriage that ended in divorce.  Toward the end of the 1920s he met and married Frida Kahlo, who was 20 years younger than him. The two artists began an unusual loving but complicated and tumultuous relationship.  They divorced in 1939 (after her affair with Trotsky), remarried in 1940, and then remained married until her death in 1954 at the age of 44.  One of her great sorrows in life, and the subject of many of her paintings (and elements in his) was her inability to bear children due to a horrendous vehicular accident during her teen years where she had been impaled on a piece of the wreckage.  She suffered greatly throughout life with resulting internal organ injuries on top of previous polio-related spine problems – enduring many surgeries and much pain.  Nevertheless, both she Diego (who described himself as “homely” and often drew cartoons of himself as a frog) had numerous extramarital affairs over the years which made their marriage tempestuous.

Both Rivera and Kahlo were both dedicated to Communist ideals – in fact Russian Communist leader Leon Trotsky and his wife lived in exile with Frida and Diego for some time.  Trotsky was assassinated in his home – just blocks from Rivera’s house and studio – after moving out over the explosive love affair with Frida. (Kingsolver)

Section 2:2 Rivera in the United States

Rivera worked in New York, Detroit and San Francisco over the period of the decade between 1930 and 1940.  America’s love affair with Rivera began in 1930, when he was invited to paint two frescos – one for the City Club of the San Francisco Stock Exchange (Allegory of California), and another for the California School of Fine Art (Making of a Fresco, Building of a City).  A third was painted for a patron in her home. Rivera worked in the United States off and on for the next decade, sometimes accompanied by Frida and other times not.

In 1931 the Museum of Modern Art (MOMA) in New York mounted a retrospective exhibition of his work – their first solo artist retrospective since Henri Matisse – a huge honor for Rivera.  He painted 8 large moveable frescos specifically for the exhibit – which broke all museum attendance records for the time. (Hurlburt 130; MOMA)

In 1932 and 1933, he completed a 27-panel fresco entitled Detroit Industry Murals in an interior courtyard at the Detroit Institute of Arts.  Commissioned by Edsel Ford, this fresco is often mentioned as the best work of his career.

In 1933, Rivera was commissioned to paint a magnificent mural on the history of man called Man at the Crossroads at the new Rockefeller Center building in New York.  As he painted, Rivera included a portrait of Lenin among the faces in the fresco.  (It was Rivera’s custom to include portraits – of political leaders, historical figures, patrons, and sometimes Frida in his frescos.) Rockefeller asked him to paint over Lenin. Rivera refused and was summarily fired.  The fresco was immediately covered with a canvas – and then, a few months later, was unceremoniously destroyed by chiseling it to rubble.

This act is still considered one of the great tragedies of modern American art. As a result of the controversy, a contract for Rivera to paint a fresco for General Motors at the 1933 Chicago World’s Fair was cancelled too.

Angry and humiliated, Rivera very publicly took his commission earnings from the Rockefeller Center project (he had been paid as per the contract) and painted a reactionary series of moveable frescos called Portrait of America for the New Workers School in New York.  The New Workers School was an ideological training center for the Communist Party of the USA that existed in New York between World Wars 1 and 2.  The mural cycle was a tribute to the history of the United States and featured portraits of Washington, Ben Franklin, Lincoln and others.

Following Portrait of America he returned to Mexico and painted another version of the Rockefeller Center mural, this time at the Palace of Fine Arts in Mexico City.  He titled the work, Man, Controller of the Universe.  Lenin made it into this version of the fresco.

For the remainder of the 1930s, Rivera worked primarily on easel paintings, drawings, and printmaking at home in Mexico.  He viewed his innovation of moveable fresco as a failure – mostly because it had failed to realize new fresco commissions for him.

In 1940, Rivera was invited to return to San Francisco to paint a ten panel moveable mural series entitled Pan American Unity for the Golden Gate International Exposition.  The panels exist today at City College in San Francisco.  It was his last fresco commission in the United States.

Rivera had always worked in other media – oil painting, drawing, and printmaking – even when his main output was fresco.    In the last twenty years of his life, he only painted one more fresco series in the U.S.  Ironically, Rivera’s political leanings – the very basis of his interest in fresco – had cost him with his U.S. capitalist patrons. His U.S. commissions dried up very suddenly after the Rockefeller Center debacle.  In the forties and fifties, Rivera painted another dozen frescos in Mexico, did hundreds of easel paintings, drawings, and other types of projects – such as large outdoor mosaic projects.  Rivera died in 1957 – three years after his life-long love, Frida Kahlo.

Section 2.3 Rivera’s Substrate Preparation and the Moveable Fresco

One of the reasons Rivera’s frescos have survived in such good condition is his attention to proper preparation of the wall.  Rivera pioneered the use of metal reinforcement for furring in his scratchcoat.  

Furring is the installation of runner bars at regular intervals (every 2 feet in his case) tied to vertical metal studs at 12 inch centers followed by the wiring of galvanized metal lath to this armature.  The scratchcoat was trowelled onto this metal lath structure.  This technique of creating a false wall on which to lay the plaster layers guarded against moisture seepage from the exterior wall and/or expansion cracks in the wall that might crack through the fresco itself. (Hurlburt 115-116; Nordmark 5-7)

Effectively divorcing the fresco from the exterior wall also allows the fresco to be carefully moved should that ever be required.  Rivera was aware that buildings in the United States typically had a shorter lifespan than in Mexico or Europe and wanted to make certain his frescos survived. 

Rivera also pioneered what became known as moveable frescos, although because of their size and weight the term moveable is somewhat a misnomer.  Other authors have called his innovation “portable murals” with the same caveat. (Hurlburt 255)

There are a number of reasons for Rivera’s interest in developing a moveable fresco substrate.  First and foremost, relatively few people could see a fresco artist’s work since it was permanently installed at one location.  While the same is true today, the fact that eighty years ago people traveled much less than we do today further isolated fresco work.  A fresco artist in the 1920s and 1930s had only black and white photographs for portfolio use.  Kodachrome film for color photography wasn’t invented until 1935 – and then for several years was only available as 6 and 18mm movie film.  

This was one but one of the difficulties Rivera faced when marketing himself for new commissions in the United States.  In addition to the difficulty of showing one’s work to potential patrons, museum exhibitions mounted at one museum and meant to travel on loan to others couldn’t include fresco art.

Rivera’s first real moveable fresco was his third commission in San Francisco in 1930 – 1931.  It was also the only fresco he ever painted in a private home.  Rivera had galvanized metal lath specially constructed for the project so that it could be moved if necessary. The work, Still Life and Blossoming Almond Trees, was done in 8 painting sessions on the client’s dining room wall.  Probably because he couldn’t fully control the temperature and humidity in the client’s home, part of the mural dried too quickly and the colors didn’t adhere properly.  (Hurlburt 111, 129)

In 1931, Rivera painted 8 moveable frescoes for his solo retrospective show at the MOMA.  In 1933, after the Rockefeller Center episode, he painted a series of 21 moveable frescos for the New Workers School in New York.

Finally, in 1940, Rivera was commissioned to paint a fresco called Pan American Unity – a ten-panel fresco – in San Francisco.

Section 2.5 Rivera’s Fresco Palette and Pigments

Diego Rivera was a purist when it came to the traditional buon fresco technique.  While some of his contemporaries – fresco artists like Orozco – used opaque whites made by mixing colors with carbonate of lime or that day’s lime putty, Rivera instead employed the traditional technique. He used the white of the plaster ground to show through the semi-transparent colors for highlights. Like fresco painters from historical times, this technique more closely resembles watercolor than oil painting – the artist gradually builds up richness and luminosity this way.  The technique involved building layer upon layer of transparent color over an monochromatic underpainting that’s been carefully modeled to create volumetric figures. (Hurlburt 39-49, 254)

Like historical fresco painters, Rivera’s palette consisted primarily of organic earth colors – many of them the exact colors known for hundreds of years.  His typical fresco palette included:

• yellow ochre
• golden ochre
• dark ochre
• raw sienna
• Pozzuoli red (Italian red earth)
• red ochre
• Venetian red
• almagre morado (red oxide of iron)
• burnt sienna
• transparent oxide of chromium
• cobalt blue
• vine blue (from calcined grape seeds)
• vine black

From these dozen or so colors – hand ground at the site by his assistants – Diego Rivera painted his magnificent masterpieces. (Helm 43-44; Ruskin and West 4)

Section 2.6 Rivera’s Fresco Technique

The buon fresco technique used by Diego Rivera is the exact technique used by Michelangelo to paint the Sistine Chapel in the fifteenth century. (Ruskin and West 4)

Rivera used marble dust instead of sand for both his browncoat and intonaco coat.  His recipe of 2 parts marble dust to 1 part lime gave him a glowing, super smooth surface on which to paint. Since his palette didn’t include white – he used the white of the wall to create highlighted areas (much like a watercolorist uses the paper for the same effect) – this bright smooth surface was a requirement. (Hurlburt 259) 

MacKinley Helm, in his book Modern Mexican Painters, recalls interviewing an assistant to Rivera to learn about Rivera’s technique.  The assistant recalled that Rivera preferred sand from mines rather than rivers because it was more fungus free.  He also insisted that the sand be washed in cyanide to further guarantee purity.  Finally, his lime was slaked for at least two months to insure that it was ready to be used for fresco.  This strict adherence to his technique is credited as saving Rivera’s walls from fungus. 

Rivera’s plasterers laid the browncoat and then permitted it to dry for at least a month so that it became resistant to humidity.  After a month had passed, the wall was ready to be painted.  On the day before an area was to be painted, the plasterer brushed the browncoat layer with distilled water.  

The next day, his plasterer spread the intonaco layer onto the area Rivera had decided to paint that day. Just as this layer began to set up, the assistant finally applied a thin layer of pure lime paste with a trowel. It was on this layer that Rivera painted – he believed that it enhanced the brilliance of his colors. 

Rivera’s cartoon technique varied over time and with each project.  Sometimes he drew directly on the surface of the wall at the moment he began to paint.  This technique eventually gave way to a more traditional approach.  Rivera drew his walls on the rough coat followed by assistants who then traced the drawings onto transparent paper.  Once the intonaco coat had been troweled on the wall, the assistant then transferred the drawing back using the traditional perforating and pouncing technique.  (Helm 43)

Rivera was a master of matching color and composition from one day to the next.  In fact, his daily cutlines conform so well to his paintings’ compositions that restorers have to use special light to find the daily junctures. (Hurlburt 254)

For his 1930 fresco at the San Francisco Stock Exchange Luncheon Club, Allegory of California, Rivera employed two painting assistants and a plasterer.  In his book The Mexican Muralists in the United States, Hurlburt interviews one of Rivera’s painting assistants.  He said that “they worked to grind the colors, trace the drawings, and very occasionally to paint unremarkable parts of the painting.  We also tidied up and generally helped to keep everything in order.” 

One of Rivera’s models for this fresco recalls him sketching on the browncoat in sanguine chalk in “a colossal scale” while standing on a soapbox. (102)

In both San Francisco murals, Rivera relied on many Renaissance fresco conventions he had studied in Italy.  Among them are a triptych format, the utilization of a vanishing point near the floor, and the inclusion of donor and friend portraits. (Goldman and LeFalle-Collins 33; Ruskin and West 5)

A good number of authors on Rivera mention a personal habit that habitually annoyed his team of assistants.  Ruskin and West, in the copy for the Detroit Industry Murals book, write, “… to the exasperation of his assistants, Rivera often dawdled after being advised that a section was ready to paint.  Knowing that timing was critical at that juncture, he chose to court the risk of the plaster drying because pressure, he discovered, led to ‘more spontaneous style.’” (4)

Lucienne Bloch, an assistant to Rivera for several projects, recalls this frustration in an interview.

I once asked him: “You know, it is three hours now since the men have called and told me that the wall is ready, and I told you.  Three hours and the wall is going to be dry,” I said.  “Why do you always wait so long?” And he replied, “I am giving myself problems, because under pressure I work better.” (Hurlburt 254)

In 1931, the Museum of Modern Art (MOMA) in New York mounted the Diego Rivera Retrospective exhibition.  In order to capitalize on the spotlight to showcase his fresco work, Rivera painted 8 new portable frescos for the exhibition – the first time any museum had shown portable fresco. (Indych-Lopez 10)

Actually, “portable” is somewhat of a misnomer in that these panels consist of a heavy steel frame and a latticework substrate covered with concrete and then several layers of plaster. Each fresco was 6 by 8 feet in dimension and weighed half a ton when complete. (Indych-Lopez 78, Hurlburt 123)

To complete the frescos in time for the show, Rivera employed 3 assistants.  They all worked 15 hour days in unheated room to prevent the plaster from drying too quickly.

American Works Progress Administration (WPA) fresco painter Lucienne Bloch worked as an assistant to Rivera for several of these projects.  For the MOMA frescos and the Detroit Industry Murals, Bloch ground pigments for Rivera.  She also worked on the Rockefeller Center project – grinding pigments and transposing cartoons to the walls.  Bloch was also a photographer – interestingly, her photograph of the Rockefeller Center mural in progress is the only photograph of it that exists. After the Rockefeller Center project suddenly ended, Bloch worked with Rivera in New York as he created the 21 moveable frescos for the New Workers School.  She went on to use Rivera’s fresco technique to paint her own murals.  A young Ben Shahn, later a celebrated artist in his own right, also worked as a Rivera assistant. (Vishny 23-24; Linsley 48)

The Detroit Industry Murals were painted in a garden court at the Detroit Institute of the Arts, where Henry Ford’s son Edsel was the President of the Detroit Arts Commission and the patron of the project.  The subject of these frescos, 27 panels in all, was different from Rivera’s previous work.  Instead of epic historical allegory, this fresco was to depict the industry and technology – celebrating Detroit and the Ford Motor Company.  Rivera had never seen such industry and was utterly fascinated by it – spending many hours in the River Rouge Ford Plant taking photographs that he used in his fresco.  (Ruskin and West 4)

Rivera required all the plaster from the garden court walls to be removed.  Next he had a grid of galvanized reinforcing bar installed to stabilize the paintings and facilitate moving the frescos, should that ever be required.  Throughout his career, Rivera was careful to have these “false walls” built whenever possible to prevent any capillary action through the wall or cracking that might destroy his painting. Next the layers of plaster were applied to the courtyard walls in the traditional manner.  When the browncoat was dry enough to be drawn on, Rivera sketched directly on it.  His painting assistants traced the drawings with translucent paper since the drawing would eventually be covered with each days’ intonaco layer of plaster. (Ruskin and West 4)

In this project, Rivera drew the entire room – all 27 panels – on the browncoat before he began to paint.  The charcoal cartoons, once they had been perforated and pounced by assistants, were pinned to the scaffolding for Rivera’s reference while he painted.  He connected the dotted lines with paint, then created the volume of the objects and figures with blacks and grays before he added the color on top of this monochromatic underpainting.

In Detroit, Rivera generally began his work late at night. Hurlburt writes, “He underpainted in black and white (sic) and towards dawn he would begin mixing color and as the light grew brighter he would add the color over the underpainting.” (136-137)

For this project, Rivera employed 7 assistants.  Each had specific jobs  – like in the Ford Motor Company assembly lines that were his subjects.  His chief assistant did most of the plastering, pouncing the sketches to transfer them to the wall, and drawing the sinopia (red ochre in this case) outlines.  Another painting assistant took Rivera’s original smaller sketches and enlarged them to the full-size cartoons.  Yet another was in charge of grinding pigments – in fact, this assistant was a Ford chemist who had approached Rivera wanting to work on the team and then went on to work with Rivera on the Rockefeller Center and New Worker’s School murals as well.

Assistants in charge of the plaster preparation generally worked the noon to midnight shift on this job; Rivera painted from midnight to noon. 

He used cartoons in a very traditional way on this project.  First, an assistant pinned them to the panel Rivera was about to paint.  The assistant then perforated them with a spiked wheel tool and pounced them with red ochre to transfer the design to the wall.  Rivera first painted a light line over the sinopia, and then began his monochromatic underpainting. (Hurlburt 136, 141)

Rivera’s murals at the Detroit Industry of Arts are considered by many to be the greatest example of the art of fresco in the United States.  

In 1932, Rivera was chosen by Nelson Rockefeller to paint a large fresco in the entrance to his new grand building, the Radio Corporation Arts Building in Rockefeller Center in New York City.  The theme of the wall, Man at the Crossroads Looking with Hope and High Vision to the Choosing of a New and Better Future, was given to Rivera by the patron.

The high-profile commission energized Rivera.  He and his assistants worked at a fevered pitch on the mural, covering up to four square yards of plaster a day and sometimes worked for 24 hours at a time. 

For this fresco, Rivera’s assistants enlarged his drawings and pounced them on the browncoat.  Rivera then finalized his sketches using red ochre.   Finally, an assistant traced Rivera’s final drawings to create the final cartoon.  That night, his plasterers applied the final smoothly polished intonaco layer and the final cartoon’s image was perforated and pounced on the wall. The wall preparation took at least 12 hours before Rivera applied the first brushstroke.  Each day after Rivera was finished, assistants began grinding pigments (his palette for this fresco was 14 colors), moving scaffolding, and transferring drawings for the following day. 

However, in May 1933 when Rockefeller asked him to replace Lenin’s head with a generic man – Lenin’s portrait had not been in the original sketches – Rivera refused.  Instead he offered to paint Abraham Lincoln’s portrait on the other side of the fresco.  Rockefeller, who had asked both Matisse and Picasso to paint the mural (they turned him down) before his mother suggested Rivera, paid Rivera, had the wall covered with a canvas, and some months later had it chiseled off the wall and carried away in wheelbarrows. (Hurlburt 166)

Rivera’s next project was to use the Rockefeller commission to fund his painting of a mural cycle of 21 portable frescos for the New Workers School in New York.  These frescos, called Portrait of America, were smaller than the ones he had painted for the MOMA exhibition – each of these was smaller than 6 by 6 feet.

Artist assistants made the fresco panels by applying a cement plaster coat onto a wood and composition board armature.  Before the plaster was dry, a wire mesh was stapled into the plaster.  The panel was allowed to cure over a period of a week, after which the traditional browncoat layer was troweled on.

For this series, Rivera worked out his compositions directly with charcoal on the panels’ browncoats.  He worked without preliminary sketches or cartoons. When he was dissatisfied, he simply took a rag and wiped out the area he wanted to rework.  When he was satisfied, he traced over the line with a red pigment wash.  Assistants would then trace a cartoon of his work, then add the intonaco coat, and after a short wait, pounce the cartoon. (Hurlburt 191, 192)

In the morning, Rivera began the day’s work by drawing over the dotted lines with the red wash.  He spent the rest of the early part of the day modeling his monochromatic underpainting.  Often it was after lunch before he began to add color. The New Worker’s School was dissolved in 1943 and Rivera’s frescos were donated and successfully moved to the headquarters of the International Ladies Garment Workers Union. (192-193)

In 1940, Rivera painted his final fresco series in the United States after spending the previous six years working exclusively in Mexico. This commission – a mural cycle in San Francisco – consisted of 10 moveable frescos entitled Pan American Unity.  His subject was the contributions of both Meso-America and Europe to the North American continent – was painted in his typical celebratory and optimistic epic style. The fresco was the largest he’d ever painted in the U.S. (22 by 74 feet) and for the first time in his career, the public was invited to watch him work.  Rivera had three women artist assistants on the project. (Rochfort 171)

Rivera hadn’t worked in fresco much since the Rockefeller Center debacle and was happy to be back in San Francisco, where he had good memories of his fresco projects there from a decade before. (Downs and Sharp 309-310)

He and Frida remarried during the time he painted Pan American Unity.  The commission also reignited his love for fresco – he returned to Mexico to paint close to a dozen more between 1940 and 1957.  He also accepted a professorship at the new Academy of Art at La Esmeralda and began to seriously collect folk and pre-Columbian art objects.  His collection numbered some 60,000 objects at the time of his death. (Kettenmann 71-72)

The latter period of Rivera’s life was a very productive one, with a dozen more frescos painted in Mexico and hundreds of drawings, easel paintings, and graphics projects.  He did several large outdoor mosaic murals that still exist – one on a movie theater in Mexico City and another in Acapulco.  His politics again became a polarizing force as he adopted a pro-Soviet stance after World War 2 and some of his later work can be seen as propagandist.  He was readmitted into the Mexican Communist party in 1954. (Hurlburt 296)

Conclusion

The painting of walls for decoration, inspiration, or to record events has been an important part of the history of the human race.  That the fresco techniques and methods developed almost a thousand years ago are still essentially the same today is a marvel to me.  As we’ve often seen in “The Chemistry of Art” class this semester, historical figures – chemists and artists – time and time again figured out how to make something by trial and error before they ever fully understood the science behind their discovery. Fresco painting technique is no exception. In addition, the chemistry of fresco is one painting technique that actually protects the work from the passage of time rather than the other way around.

Fresco also appears to be enormously hard work requiring an unusual dedication to seeing a project through to completion.  With each day’s painting archived by a cutline, some of the enormous Renaissance frescos are known to have taken many years to complete.

Diego Rivera has always interested me, so the chance to look at his technique on his U.S. projects was a joy.  Interestingly, more has been written about his subject matter, politics, and fall from celebrity than his technique.  I learned in my reading that Rivera’s personal papers are not available to researchers, despite the fact that his will only stipulated that they remain locked from public view for ten years after his death.  Fortunately, he was a colorful, larger-than-life character, so much has been written anecdotally about people’s interactions with and impressions of him.

Everything I read about Rivera’s painting habit suggests that he was extremely particular about utilizing the traditional preparation and process techniques of traditional fresco.  Sadly, I have not seen any of his frescos in person, but an art curator friend from Mexico City says that they are as brilliant and breathtaking as the day they were painted.  Certainly the plethora of photographs of his work bear this out.

Coincidentally to the timing of this paper, just last November MOMA mounted a retrospective of Rivera’s 1931 solo exhibit that runs for another month – through May 14, 2012.  The website for the exhibition has a plethora of video of Rivera painting, details about the preparation of the panels, preliminary sketches, and the like – much of which hasn’t been seen in public for 80 years.  Unfortunately, I didn’t learn about the exhibit in time to use the exhibit catalog in my sources for this paper, but the website ephemera is fascinating. (MOMA)

Additionally, a heretofore-unseen collection of 240 of some 6500 photographs belonging to Frida Kahlo’s estate is currently on exhibit at Artisphere in Arlington, VA.   The photographic collection was finally unsealed in 2007 – 50 years after Rivera’s death.  The daughter and granddaughter of professional photographers, Kahlo painstakingly recorded her life with Rivera in photographs.  (Artisphere)

Clearly, the public continues to be interested in learning about the foremost muralist of the 20^th Century and his celebrity artist wife.

Works Cited

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“Diego Rivera: Murals for the Museum of Modern Art.” MOMA. 1 Apr. 2012 <www.moma.org/interactives/exhibitions/2011/rivera/>

Downs, Linda and Sharp, Ellen, eds. Diego Rivera: A Retrospective.  New York: Detroit Institute of Arts in association with W. W. Norton, 1986.

Evans, Ernestine. The Frescoes of Diego Rivera. New York: Harcourt, Brace and Company, 1929.

Farago, Claire J. “Leonardo’s Battle of Anghiari: A Study in the Exchange between Theory and Practice.” The Art Bulletin 76:2 (1994): 301-330. 29 Jan. 2012 <http://www.jstor.org/stable/3046024&gt;

“Frida Kahlo: Her Photos.” Artisphere. 9 April 2012  <http://www.artisphere.com/programs/visual-arts/frida-kahlo.aspx&gt;

Goldman, Shifra M. and LeFalle-Collins, Lizetta. In the Spirit of Resistance. New York: The American Federation of the Arts, 1996.

Hale, Gardner and O’Sheel, Shaemas. Fresco Painting. New York:  W. E. Rudge, 1933.

Helm, MacKinley. Modern Mexican Painters. New York: Dover Publications, 1989.

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