Technique in painting is the sum-total of all the methods by which coloured bodies are fastened upon supporting grounds according to the wish and plan of the painter.
Thompson, Daniel V., The materials and techniques of medieval painting
The basis of the profession, the very beginning of all these manual operations, is drawing and painting. These two sections call for a knowledge of the following: how to work up or grind, how to apply size, to put on cloth, to gesso, to scrape the gessos and smooth them down, to model with gesso, to lay bole, to gild, to burnish; to temper, to lay in; to pounce, to scrape through, to stamp or punch; to mark out, to paint, to embellish, and to varnish, on panel or ancona.
The craftsman’s handbook by Cennini, Cennino, active 15th century; translated by Thompson, Daniel Varney, 1902- ed
§ 82. Painting in Tempera.
Before the time of Cimabue and from that time onwards, works done by the Greeks in tempera on panel and occasionally on the wall have always been seen. And these old masters when they laid the gesso ground on their panels, fearing lest they should open at the joints, were accustomed to cover them all over with linen cloth attached with glue of parchment shreds, and then above that they put on the gesso to make their working ground.
Giorgio Vasari (1511-1574), Vasari on technique; being the introduction to the three arts of design, architecture, sculpture and painting, prefixed to the Lives of the most excellent painters, sculptors, and architects
Preparing the panel
Materials & Tools
The main steps to prepare a support for tempera painting:
- Preparing the wood, removing all imperfections, polishing, closing holes, laying tin foil over nails or iron pins used to assemble multiple panels or wooden decorations etc.
- Laying a thin cloth (canvas) on the panel: entire panel or those areas that are most likely to crack in future (junctions between panels, knots etc.)
- Applying and polishing the ground (chalk or gesso mixed with animal glue size).
Let’s do some Alchemy!
To make size and gesso ground for tempera painting yo will need:
GLUTINUM
Animal skin glue, tipically rabbit glue was and is very widely used in painting, violin making, production of illuminated manuscripts, restoration of all the above and more.
Oak galls can be found on oak trees all around the globe. In late winter and early spring, they are easier to identify while an oak tree is leafless.
Numerous plants, such as hawthorn tree, contain tannins in various parts of the plant.
CRETA
Two compounds were used to ground panels for painting through Middle Ages and the Renaissance:
- Gypsum [calcium sulfate], also known by its Italian name gesso, or Gesso di Bologna, or Plaster of Paris
- Chalk [calcium carbonate], also known as Bianco di Spagna, sometimes simply called crea o creta in the treaties
Today both can be acquired in any Florentine art supplies shop or in a well-furnished mesticheria.
AQUA
Clean water, typically rain or spring water was used. We will use distilled water.
BALNEUM MARIAE
Bain-Marie or in Italian Bagno Maria is a process of melting and heating substances with help of a water bath (double-boiler).
Commonly used for many centuries in medicine, kitchen and all fields of craftsmanship, this process has even earned its own alchemical symbol.
For us it will be a process of heating the gelatin size with or without gesso.
Additional ingredients:
- Honey or glycerin: to make the gesso ground more elastic honey or glycerin is sometimes added.
- Preservative: vinegar, wine or today you could use a chemically produced biocide such as Nipagina (Methylparaben). If you do not intend to store the gelatin it is not necessary.
- White pigment: lead white (can be replaced with zinc or titanium whites to avoid using toxic lead) makes the surface more compact and the color more brilliant cold white.
- Colored pigments: if you want to have a colored ground, you can simply add pigments to the mixture. It would be best to first grind well these pigments with water.
Recipe and instructions
Now let’s take a closer look at a historical recipe and step-by-step instructions from the early XV century. This process (or a one very similar to it) was very commonly used throughout Tre-, Quttro- and early Cinquecento, but it actually has much deeper roots: Egyptian sarcophagi were made of carved wood gessoed almost in an identical way and then painted with pigments ground in gum arabic, egg tempera or even linseed and poppy seed oils.
Recipe 1, Italy, early XV century
Original Text
[translation]
HOW YOU SHOULD START TO WORK ON PANEL OR ANCONAS.
CHAPTER CXIII
Now we come to the business of working on anconas or on panel. To begin with, the ancona should be made of a wood which is known as whitewood or poplar, of good quality, or of linden, or willow.
And first take the body of the ancona, that is, the flats, and see whether there are any rotten knots; or, if the board is greasy at all, have the board planed down until the greasiness disappears; for I could never give you any other cure. See that the wood is thoroughly dry; and if it were wooden figures, or leaves, so that you could boil them with clear water in kettles, that wood would never give you any trouble with cracks. Let us just go back to the knots or nodes, or other defects which the flat of the panel may display. Take some strong leaf glue; heat up as much as a goblet or glass of water; and boil two leaves of glue, in a pipkin free from grease. Then have some sawdust wet down with this glue in a porringer. Fill the flaws of the nodes with it, and smooth down with a wooden slice, and let it stand. Then scrape with a knife point until it is even with the surrounding level.
Look it over again; if there is a bud, or nail, or nail end, sticking through the surface, beat it well down into the board. Then take small pieces of tin foil, like little coins, and some glue, and cover over carefully wherever any iron comes; and this is done so that the rust from the iron may never come to the surface of the gessos.
And the flat of the ancona must never be too much smoothed down. First take a size made of clippings of sheep parchments, boiled until one part remains out of three. Test it with the palms of your hands; and when you find that one palm sticks to the other, it will be right. Strain it two or three times. Then take a casserole half full of this size, and the third <part>* water, and get it boiling hot. Then apply this size to your ancona, over foliage ornaments, canopies, little columns, or any sort of work which you have to gesso, using a large soft bristle brush. Then let it dry.
Next take some of your original strong size, and put two coats over this work with your brush; and always let it dry between one coat and the next; and it will come out perfectly sized. And do you know what the first size, with water, accomplishes? Not being so strong, it is just as if you were fasting, and ate a handful of sweetmeats, and drank a glass of good wine, which is an inducement for you to eat your dinner. So it is with this size: it is a means of giving the wood a taste for receiving the coats of size and gesso.
HOW YOU SHOULD PUT CLOTH ON A PANEL.
CHAPTER CXIIII
When you have done the sizing, take some canvas, that is, some old thin linen cloth, white threaded, without a spot of any grease. Take your best size; cut or tear large or small strips of this canvas; sop them in this size; spread them out over the flats of these anconas with your hands; and first remove the seams; and flatten them out well with the palms of your hands; and let them dry for two days. And know that this sizing and gessoing call for dry and windy weather. Size wants to be stronger in summer than in winter. Gilding calls for damp and rainy weather.
HOW THE FLAT OF A PANEL SHOULD BE GESSOED WITH THE SLICE WITH GESSO GROSSO.
CHAPTER CXV
When the ancona is quite dry, take a tip of a knife shaped like a spatula, so that it will scrape well; and go over the flat. If you find any little lump, or seam of any sort, remove it. Then take some gesso grosso, that is, plaster of Volterra, which has been purified and sifted like flour. Put a little porringerful on the porphyry slab, and grind it with this size very vigorously, as if it were a color. Then scrape it up with a slice; put it on the flat of the ancona, and proceed to cover all the flats with it, with a very even and rather broad slice; and wherever you can lay it with this slice you do so.
Then take some of this same ground-up gesso; warm it; and take a small soft bristle brush, and lay some of this gesso over the moldings and over the leaves, and likewise over the flats gessoed with the slice. You lay three or four coats of it on the other parts and moldings; but you cannot lay too much on the flats. Let it dry for two or three days. Then take this iron spatula and scrape over the flat. Have some little tools made which are called “little hooks,” such as you will see at the painters’ made up in various styles. Shape up the moldings and foliage ornaments nicely, so that they do not stay choked up; get them even; and contrive to get every flaw in the flats and gap in the moldings repaired by this gessoing.
HOW TO MAKE THE GESSO SOTTILE FOR GESSOING PANELS.
CHAPTER CXVI
Now you have to have a gesso which is called gesso sottile; and it is some of this same gesso, but it is purified for a whole month by being soaked in a bucket. Stir up the water every day, so that it practically rots away, and every ray of heat goes out of it, and it will come out as soft as silk. Then the water is poured off, and it is made up into loaves, and allowed to dry; and then this gesso is sold to us painters by the apothecaries. And this gesso is used for gessoing, for gilding, for doing reliefs, and making handsome things.
HOW TO GESSO AN ANCONA WITH GESSO SOTTILE; AND HOW TO TEMPER IT.
CHAPTER CXVII
When you have done the gessoing with gesso grosso, and scraped it nice and smooth, and evened it up well and carefully, take some of this gesso sottile. Put it, loaf by loaf, into a washbasin of clear water; let it soak up as much water as it will. Then put it on the porphyry slab, a little at a time, and without putting any more water in with it, grind it very thoroughly. Then place it neatly on a piece of strong white linen cloth; and keep on doing this until you have taken out one loaf of it. Then fold it up in this cloth, and squeeze it out thoroughly, so as to get as much water out of it as possible. When you have ground as much of it as you are going to need, which you must consider carefully, so as not to have to make gessos tempered in two ways, which would not be a good system, take some of that same size with which you tempered the gesso grosso. Enough of it wants to be made at one time for you to temper the gesso sottile and the grosso.
And the gesso sottile wants to be tempered less than the gesso grosso. The reason? — Because the gesso grosso is your foundation for everything. Nevertheless, you will naturally realize that you cannot squeeze the gesso out so much that there will not still be some little water left in it. And for this reason, make the same size, confidently. Take a new casserole, which is not greasy; and if it is glazed, so much the better. Take the loaf of this gesso, and with a penknife cut it thin, as if you were cutting cheese; and put it into this casserole. Then pour some of the size over it; and proceed to break up this gesso with your hand, as if you were making a batter for pancakes, smoothly and deftly, so that you do not get it frothy.
Then have a kettle of water, and get it quite hot, and place this casserole of tempered gesso over it. And this keeps the gesso warm for you; and do not let it boil, for if it boiled it would be ruined. When it is warm, take your ancona; and dip into this pipkin with a good-sized and quite soft bristle brush, and pick up a reasonable amount of it, neither lavish nor skimpy; and lay a coat of it all over the flats and moldings and foliage ornaments. It is true that for this first coat, as you are applying it, you smooth out and rub over the gesso, wherever you lay it, using your fingers and the palm of your hand, with a rotary motion; and this makes the gesso sottile unite well with the grosso.
When you have got this done, begin over again, and apply a brush coat of it all over, without rubbing it with your hand any more. Then let it stand a while, not long enough for it to dry out altogether; and put on another coat, in the other direction, still with the brush; and let it stand as usual. Then give it another coat in the other direction. And in this way, always keeping your gesso warm, you lay at least eight coats of it on the flats. You may do with less on the foliage ornaments and other reliefs; but you cannot put too much of it on the flats. This is because of the scraping which comes next.
HOW YOU MAY GESSO WITH GESSO SOTTILE WITHOUT HAVING GESSOED WITH GESSO GROSSO FIRST.
CHAPTER CXVIII
Furthermore, it is all right to give any small-sized and choice bits of work two or three coats of size, as I told you before; and simply put on as many coats of gesso sottile as you find by experience are needed.
HOW YOU SHOULD TEMPER AND GRIND GESSO SOTTILE FOR MODELING.
CHAPTER CXVIIII
There are many, too, who just grind the gesso sottile with size, and not with water. This is all right for gessoing anything which has not been gessoed with gesso grosso, for it ought to be more strongly tempered. This same gesso is very good for modeling up leaves and other productions, as you often need to do. But when you make this gesso for modeling, put in a little Armenian bole, just enough to give it a little color.
HOW YOU SHOULD START TO SCRAPE DOWN AN ANCONA FLAT GESSOED WITH GESSO SOTTILE.
CHAPTER CXX
When you have finished the gessoing, which must be finished in one day (and, if necessary, put in part of the night at it, just so you allow your required intervals), let it dry without sun for at least two days and two nights: the longer you let it dry, the better it is. Take a rag and some ground-up charcoal, done up like a little ball, and dust over the gesso of this ancona. Then with a bunch of hen or goose feathers sweep and spread out this black powder over the gesso. This is because the flat cannot be -scraped down too perfectly; and, since the tool with which you scrape the gesso has a straight edge, wherever you take any off it will be as white as milk. Then you will see clearly where it is still necessary to scrape it down.
HOW THE GESSO SOTTILE ON THE FLATS SHOULD BE SCRAPED DOWN, AND WHAT THESE SCRAPINGS ARE GOOD FOR.
CHAPTER CXXI
First take a “little hook” with a straight edge, one finger wide, and go lightly all around the flat, scraping the molding once. Then take your spatula, ground to as straight an edge as possible; and with a light touch, not holding the point tightly at all, you rub it over the flat of your ancona, sweeping the gesso ahead of you with these feathers. And know that these sweepings are excellent for taking the oil out of the parchments of books. And in the same way scrape down the moldings and foliage ornaments with your little tools; and smooth it up as if it were an ivory. And sometimes, if you are hurried and have several jobs on hand, you may just smooth up the moldings and foliage ornaments with a linen rag, soaked and wrung out, rubbing it well over these moldings and foliage ornaments.
Additional information
As you can see, the process of grounding panels for tempera painting as described by Cennini takes more than one full day. In fact, 2 coats of size 1or 2 coats of gesso grosso and at least 8 coats of gesso sottile and then scraping and smoothing of the panel would require 3 to 5 working days.
For this reason we will have to simplify the process as much as possible to make it fit the tight schedule of this course.
Recipe 2 (modern, based on historical recipes):
Ingredients:
- Rabbit glue
- Distilled water
- Gesso di Bologna
Step 1: Prepare the SIZE
Soak the glue overnight in a 20% solution (1 part glue 4 parts distilled water). Next day, heat the glue au bain-marie until it fully dissolves.
Make weaker solutions:
- 10% solution is made by taking 1 part of glue and adding 1 part water to it.
- 5% solution is made by taking 1 part 10% solution and adding 1 part water to it.
- You can also make a 15% solution by taking 1 part 10% solution and adding 1 part 20% solution and so on.
Step 2: Apply the size and lay the canvas
First size the panel with 5% solution and, when dry, size your panel with a 10% solution and let it dry.
Soak the canvas in 15% hot size lay on the panel, remove all bubbles and folds and let it dry.
Step 3: Prepare the Gesso
Then prepare the gesso using 2 parts of your 5% solution and 3 parts of gesso sifted directly into the pot with the hot size. Stir very gently with a stick or a back side of your brush.