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:
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.
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.
Clean water, typically rain or spring water was used. We will use distilled water.
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.
- 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
Recipe 2 (modern, based on historical recipes):
- 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.