The Practice of
Tempera Painting - Carriers & Grounds (cont.)

This second size coat must be allowed to dry like the first, at least overnight. Do not try to hasten these drying processes. When you are perfectly familiar with the behavior of the materials, you may want to risk taking short cuts in an emergency; but they are always dangerous. The drying of size is not an altogether simple business. It really takes a good many days for a coat of one of these mixtures to get into a state of equilibrium with the panel and the atmosphere; and the stability of the ground will be seriously jeopardized if you try to hurry it. It is better to allow several days more than these directions call for than even a few hours less. Time is an essential ingredient. And it is seldom indeed that one's drawings and studies are so perfectly in order that one cannot spend a little time on them with advantage while these preparations are under way. The way to save time is to make one of these waiting periods do for several panels; that is, by gessoing several panels at one time, the hours and labor may be made to go much farther. It is about as easy to gesso six panels as one, and it can be done almost as quickly. [pp. 22-23]

The Intelaggio
After the second sizing, it is a good plan to fasten strips of well-washed linen cloth over the glued joints, so that if there is any shrinkage, the gesso will not give way in those parts. It is, indeed, a good plan to lay linen over the whole surface of a wooden panel; but it is not necessary, only an added safeguard against cracking. Do not try to put the linen over your moldings; it is apt to do more harm than good. The linen must be old, or it may shrink; but it must not be worn out. An old damask napkin is good. Cut it into strips, soak them in a hot solution of half an ounce of gelatine in five ounces of water, and then lay the one by one over the joints that you wish to guard, pressing them down firmly into position, and rubbing out as much of the size as you can with your fingers. After the size has set, rub over them again, to be sure that they are firmly in place. Allow this cloth coat, or intelaggio, at least twenty-four hours for drying, and preferably two or three days. [p. 24]

Puttying
Before you apply the gesso, you may have a certain amount of puttying up to do, especially on panels with moldings attached. The holes caused by countersinking should be brought up flush, and there are apt to be scratches, marks, or blemishes in the moldings and even on the flat, which should be filled up at this stage. Mix up some whiting with a little of the stock gelatine solution [one ounce of gelatine in sixteen of water], until it is about the consistency of rather soft putty. The most convenient way to mix a small amount is to put a spoonful of whiting into the palm of your hand and add the size to it there, stirring it and working it about to make a soft and rather sticky paste. Roll it up into a little ball, and as it cools it [p. 24] will set, so that it can be handled quite cleanly. With a knife or spatula work this putty generously into the nail holes or scratches or other places which need puttying. Do not try to leave the surface quite smooth. It shrinks a little in drying, and so should be a little convex when it is first put on. Let it dry for at least two hours; and then scrape it smooth with a knife.

If there are no ornaments to be applied, you may proceed with the gessoing after the first size coat, if you are feeling hurried. It is better, however, to put on a second coat of size in all cases, and particularly in those in which there is to be some burnished gilding. For brush work [which does, unfortunately, have to be taken into account], the puttying may be done over the first size coat, and the second size coat omitted entirely. In this case, the putty should be mixed up quite moist and sticky; and it must always be given at least an hour or two to dry before the gessoing is started. [pp. 24-25]

The Simplest Gesso
The gesso mixture may be made as follows. Take eight ounces of the stock solution of gelatine [one to sixteen, you will remember], and heat it in the double boiler. For this purpose, the bottom of the double boiler should contain as much water as possible, so that it will stay hot for some time after it is taken off the stove. While the size is getting hot, weigh out twelve ounces of the finest gilders' whiting, that is, an ounce and a half of whiting by weight for each ounce by measure of the solution of size.

Take the double boiler off the stove, so that the water in the bottom part will keep the size solution hot, but not too hot. Once the gesso is mixed, it must be kept as cool as it is possible to work with it. Sprinkle the whiting on to the surface of the hot size without stirring it. Simply allow it to sink into the solution. Avoid throwing in large quantities at once, or they may drag bubbles of air down into the mixture. At first the whiting will be soaked up readily; but toward the end you will find it necessary to aim the whiting at the edges of the liquid, as the pile of material soaked up rises in the center. A teaspoon is a convenient implement for sprinkling in the whiting. [p. 25]

Work as quickly as the soaking up of the whiting will allow you to. If the size were to get cold, you would be in trouble; but this need never happen. When all the shifting is in, let it stand until it has all become moist with size. If there is a ring of wet around the outside, and a pile of dry whiting in the center, brush the powder lightly off on to the edge of the liquid. When all the whiting has soaked up or become damp, the mixture is complete; it needs only stirring and straining to be ready for use.

The best tool for stirring the gesso is a brush. Slip your brush very gently into the mixture, and move it slowly around the sides and bottom of the dish, gradually turning the material over and mixing it; but take care to avoid beating it or getting air bubbles into it. The chief purpose of this stirring is to mix in the crust of almost solid whiting at the top with the comparatively liquid gesso below. It can be omitted; for the straining mixes the material. But it is better to stir a little, carefully. Pour the stirred mixture out into another container, and wash the brush and the top part of the double boiler. [p. 26]

Stretch one or two thicknesses of cheesecloth over the top of the double boiler, and fasten them there with a string or wire bound around the edge under the lip. Pour the gesso gradually upon the sieve so formed, and very gently urge it through by coaxing it with the brush. When it is all strained, remove the cheesecloth, wash the brush again, and stir the gesso with it. [pp. 25-27]

The Secret of Success
By the time the gesso has been strained, it will probably be so cool that it will soon set to a jelly. When this happens, place it over the hot water for a moment, stirring it slowly but constantly with the brush, and it will become liquid again in a moment. As soon as it is liquid, take it off the hot water. Never let it stand over hot water a second longer than is absolutely necessary, or you will find your gesso full of air-bubbles, if not of worse defects. The importance of this simple precaution cannot be overemphasized. [p. 27]

Application of the Gesso
The object in applying the gesso is to get on a fairly considerable thickness of it as smoothly and evenly as possible. There are several ways of doing this, the simplest and best, perhaps, for a beginner being to paint it out in squares, exactly as recommended for applying the size coats. if you follow this method, you will begin painting out a square with brush strokes running from left to right and strake it off with strokes form top to bottom; and continue in this way until the whole of the panel is covered. Then for the second coat begin with a square half the size of the first, so that the edges of the squares in the second coat will not coincide with those in the [p. 27] first. In putting on the second coat, reverse the order of the brushing; that is, begin with strokes running from top to bottom, and strake off with strokes running from left to right. This will make your finishing strokes in the second coat cross those of the first coat, and tend to make the surface even. In the third coat, you return to the order of strokes used for the first. Normally, five coats will be needed.

Unlike the preliminary size coats, which have to dry thoroughly, the coats of gesso must follow one another as rapidly as possible. You must never apply more gesso to a gessoed panel which has had time to dry completely. The successive coats must be applied while there is still enough moisture in the previous coats to make the whole lot bind together into one uniform system. The proper moment for a second coat of gesso is when the first coat has just dried "dull" all over. When the gesso is first applied it looks wet and shiny as you look across it toward the light. As it dries, this shininess disappears. You must wait between coats until the last trace of shine is gone; but not until the gesso is really dry. This distinction is perfectly easy to make in practice, and you will have no trouble with it.

The number of coats of gesso to apply depends a little on how thick the coats are, and also on whether there is to be any burnished gilding. For painting without gilding, a thinner gesso layer will do than is required for good burnished gold. If the gesso is applied, as it should be, with a generous hand, not excessively, but rather more thickly than house paint, and neatly, so as not to require too much scraping, five coats will make a good normal gesso for all purposes. It is always better to have the gesso a little thicker than need be on the flat of the panel than to risk scraping through to the wood; but on moldings a whiting gesso will choke up fine detail after the third coat, and may be used more sparingly. [pp. 27-28]

An Alternative Method
Instead of brushing all the coats out in squares, these "brush coats" may be alternated with what are known as "tap coats," To apply a tap coat, the brush is filled with a generous supply of gesso, [p. 28] and then tapped or smacked against the panel, while at the same time it is pushed gradually forward, away from the worker. The brush must always be moved forward, never back toward the worker. It must be kept fairly full of gesso; and the surface of the panel is to be gone over with this combined pushing and taping motion until it is covered with an even soft stipple, produced by the lifting of the brush. These tap coats possess two advantages: first, that they b ild up the thickness of the gesso rather more quickly than brush coats, and second, that they tend to obscure the marks of the brush, and so to reduce the labor of scraping. They may be used for the second and fourth coats, the first, third, and fifth being brush coats. It is possible to apply a brush coat immediately after a tap coat without waiting for the tap coat to dry dull. In this case, it is not painted out in squares, and not straked afterward, but simply painted on rather generously immediately after the tap coat is finishrd. For frames and moldings, particularly, this is the best system. In gessoing a molding, take pains to prevent unnecessary choking up of the hollows and be a little extra generous with the gesso on the tops of the forms and the "points of wear." Do not bury the forms of your moldings or carvings under a shapeless mass of plaster. Remember that imperfections which would be intolerable in a plane surface will pass unnoticed in a modeled surface. Shapes can be restored by tooling out the gesso, but that sort of labor can be largely reduced by taking care in the gessoing. [pp. 28-29]

Scraping the Gesso
When the five coats, or more, or less, have been applied--all in one day--let the panel dry as usual for a day or two, the longer the better. It is then ready to be scraped smooth. Begin scraping the flat of the panel. The best tool for this purpose is a steel scraper with a straight edge, two or three inches wide. This scraper may be made of a plane blade, or simply of a strip of thinnish steel. The corners should be rounded off on the grindstone, and the edge made absolutely straight across. It may then be ground sharp, with a chisel edge, and given a slight burr by rubbing the edge over toward the back against a piece of harder steel. Another way of putting a burr on it is to hold the blade vertically on an Arkansas oilstone, and rub it hard against the stone in the direction of the edge of the blade, from end to end. [p. 30]