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How To Paint In Fresco

( Originally Published 1937 )

THE increased interest in the beautiful and ancient art of fresco painting is a particularly encouraging sign. The medium is of the highest artistic value, requiring a greater degree of judgment and organizing ability than any other forms of painting. It excels in the fact that it truly becomes a part of the wall, rather than a skin or covering. Architecturally, this is of great importance, only mosaic decoration exceeding it in this respect. It is a medium that is peculiarly adapted to the country, its primitive materials, and simple, direct technique tying it by association with the earth and nature. The clear air of the country is perfect for the preservation of frescoes, their greatest enemy being the impure, acid-laden atmosphere of cities.

Most of the rooms of the country house are potential settings for fresco decoration: in the living room, an over mantel panel; in the kitchen and bath-room, friezes or borders; in the playroom or nursery, the walls may be covered with pictures of animals and legendary characters, painted there by the children themselves.

Roughly outlined, the process is this: on a suitably prepared foundation is laid a thin coating of a mixture of slaked lime and marble dust. The painting, in unchangeable earth colors ground with water only, is applied to this surface. The color, being absorbed by the plaster, becomes imbedded in the calcium carbonate, formed from the slaked lime (calcium hydrate), when it reacts with the carbon dioxide of the air.

Thus the lime reverts to its original condition as limestone (calcium carbonate), from which it was altered when the burning drove away its own carbon dioxide. It takes time for all the lime to be re-crystallized, but a skin begins to form at the surface as soon as the plaster is laid, and the colors will not penetrate the film once it is complete. For the artist this is a challenge: he is obliged to finish within a few hours whatever painting he starts.

The fresco painter is not obliged to work on walls. I have had interesting results allowing students to apply the plaster to panels of galvanized metal lath or sheetrock nailed to a rigid frame with galvanized nails. The side of a kiln or chimney is also a tempting place to try out fresco ideas. If they don't work, plaster them over.

For serious work, the wall must be so prepared that it does not get damp; dampness is the worst enemy of fresco (apart from the presence of sulphur in the air, as in smoky cities like Pittsburgh). The wall on which the fresco is to be painted should be separated by an air space from the outside wall.


The ground for the fresco is built up by at least three coats of coarse plaster, the first made of broken brick or pottery mixed with sand and lime; the second the same with a smaller aggregate, and the third coarse sharp sand and lime. The coats are finished rough with the wood float. The total thickness should be greater than an inch. Some of the old Roman and Pompeiian frescoes had grounds up to five inches thick.

Now comes the preparation of the finished surface called the intonaco. On its mixing and application depends the success of your work. The best lime is made in the old-fashioned wood-burning kiln, a sort of vertical flue built into a hillside.

Lacking this kind of lime, use the powdered product of commerce coming in 50 lb. paper bags. You can buy either quicklime or slaked (hydrated) lime this way and if you are short. of time, use the hydrated. Put it into water and stir it every day for a week, storing it in a tub or crock closely covered from the air. Then put it through a sieve and let it settle. Season for three months or longer and replenish from time to time the layer of water that covers the lime paste, so that the air never has access to it.

Today most lime is burned with coal and there is a danger of sulphur from the coal combining with it in the burning, and later causing efflorescence on the wall. Where you suspect this danger wash the intonaco with a solution of barium carbonate as soon as it is laid on the wall, before painting.

When you are ready, mix with the lime paste some pure white marble dust. This is best if the particles are graded in size, the small pieces fitting between the larger ones. Have slightly more than enough lime paste to cement these particles together, allowing for the lime's drying shrinkage. Determine the proportion by experiment. The "marble dust" should be fine, clean grains, like table salt. Some fresco painters use fine white silica sand either to replace part of the marble or all of it. Start with equal parts lime paste and marble. If the mixture sticks to the steel float instead of coming away clean, more marble is needed. Too much lime causes the intonaco to crack. Once the mixture is decided on, mix up enough for the whole job and store it in crocks or tubs, covered with water. It cannot be mixed too much. Beat and cut it down with the edge of the trowel many times until it is smooth, unctuous sludge. Be-fore applying it, wet the wall. Spread the intonaco with the wood float, and wet it often while you polish it with the steel float. Use small trowels and palette-knives in narrow places.


Draw the design to scale: 1 1/2' to the foot. The figures are to be seen as spots of color, not as individuals, as we are concerned with color relation-ships at this stage. (With larger scale drawings, you come to the actual work stale, having completed your creation in the preparatory study.) Then make full-size cartoons of all the figures and objects in the study—tone studies in charcoal, sanguine chalk or wash. From these make tracings on thin paper.


The only colors suitable for fresco are earths and neutral mineral colors unaffected by lime. The lakes, owing their color to organic derivatives, are out, of course. Colors that are compounds of sulphur, such as cadmium yellows, vermilion, and ultramarine blue, must never be used.

Purchase the dry colors from a good colorman. Dealers in stucco and plaster specialties sell "Lime proof colors." I used some on a fresco three years ago, and they have stood up very well. One is a bright red, resembling vermilion. Guaranteed by a reputable house for, use out of doors, they should be quite satisfactory for fresco.

The colors lighten on the wall after they dry. To judge the tones they should be matched to your color sketch by mixing them dry first. For white, dry some of the slaked lime in little cakes, and crush them to a powder. Match the tones to your sketch; grind the powders in water with a muller on a slab; and put them in glass jars labeled to indicate the pigments contained. A stroke of the color should be applied to the label.

Grind the colors for the whole job before you start the painting. Then put out in saucers on a board, enough for the day's work, with a supply of your white remixed to a paste, and a bowl of water. Paint a stroke of each color on the board, to remind you of its effect when dry.

Enlarge on the ground the rough outlines of your composition, from the scale drawing, with squares or diagonals. Paint or scratch them clearly so they cannot be effaced.


Work from top to bottom, finishing the upper parts first. The plaster and color drip and spoil any-thing below. Start at either the right or the left upper corner. Lay on to a thickness of about 1/8" to 3/16'', as much intonaco as you can cover in a half day; later you will find whether conditions will permit working longer on one area. Apply to the fresh plaster the tracings of your cartoons, and trace the outlines with a blunt point to transfer them to the wall. Then start to paint, with your color sketch and cartoon handy.

Try to paint it at first go. The technique must be transparent like water-color. No overpainting is possible. Do not try to build deep shadows by putting one wash on top of another, for the effect of this is to lighten instead of to darken the color when dry. A satisfactory method is to paint in the highlights first, then surround them with the half-tones and then paint in the shadows. I have experimented with applying the colors with an air brush and compressed air, but I believe that this technique is not adapted for fresco, although it gives beautiful gradations of tone, and clean-cut outlines (by spraying the paint against a cardboard shield, cut to match the outline of the cartoon). The tendency was for the color to pile up on the surface in amounts exceeding the capacity of the intonaco to absorb it.

If you make mistakes—and everyone does—cut out the offending part, lay in some fresh intonaco and paint it over again. See that you burnish it well into the rest with the steel float, wetting it as much as necessary.

Stop your work where there is a definite change of tone or color in the design, even if this means spreading out into complicated shapes of fresh intonaco against uncovered ground. It is impossible to join areas without showing. It is a good plan to indicate part of the background against a figure the better to judge its values. Next morning, trim back the intonaco to the outline, and lay in fresh, for the final painting of the background. This keeps the edge of the outline moist so that the new joins better to the old. The trimming should be done slantwise to make a longer joint, with a sharp knife like a surgeon's scalpel.

Work boldly and freely, and forget the slower processes of oil painting. And have a good time doing it.

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