Using a medieval recipe
What is gesso?
On day four of my medieval illuminating course, we work the whole day with gold leaf, shell gold and other leaf metals. One of the gold grounds (adhesion layers for the gold) is gesso, but what exactly is it?
Gesso is a substrate of lime or plaster bound with a glue used by artists to prepare wood, painting canvas or other material for painting. There are several medieval recipes for making gesso. These recipes often used animal glue such as fishglue or parchment glue to bound the plaster. Several layers were often applied and each layer was sanded. This created a beautifully smooth surface and has the advantage that the paint does not soak into the undercoat. You can compare gesso somewhat with a primer. Modern gesso is often made using an acrylic as a binder of the lime or plaster and is thus really different in composition from the medieval variant.
Illuminators of manuscripts also used gesso but as a raised layer to apply gold leaf on top. Because of this elevation, the reflection of light creates a brilliant shiny gold layer. At first, medieval manuscripts applied gold in a flat manner. Later from the Romanesque period and especially in the Gothic period, a raised gesso layer was used to enhance the lustre of manuscripts.
There are many recipes of gesso and although the basic ingredients are always the same, you can change the proportions between them to your own taste.
What do we need?
- A frosted glass plate about 30 x 40 cm in size, with a rough (sandblasted) side, also called satin glass.
- A small spoon.
- Plaster.
- Finely ground white candy sugar.
- Scalpel knife.
- Two palette knives.
- Lead white. (Be very careful with this, use a good quality dust mask!) You can also use titanium white.
- Armenian bolus. (Red-) (*)
- Distilled water.
- Fish glue, liquid.
- A glass muller.
- Greaseproof paper or baking paper.
- A piece of thick cardboard.
- A sheet of thick white paper.
- Some white tissues or a kitchen roll
How to do it
- Make sixteen heaps of plaster on the glass plate using the spoon.
- Then, in the same way, apply two spoonfuls of white sugar candy. The candy sugar makes the gesso hygroscopic, i.e. the mass attracts moisture and makes it sticky.
- Then add six spoonfuls of lead white (may also be titanium white). The white lead serves to make the gesso flexible. Use latex gloves and a dust mask when using white lead and wash your hands well after working!
- Mix everything well with the palette knife.
- Add a pinch of Armenian bolus (*) for colour, the whole thing will now take on a light pink colour.
Mix everything again and make a heap with a dimple in the middle. Pour a little distilled water into the hole. Stir everything until a nice smooth mixture is formed, a kind of paste.
6. Then mix in a spoon and a half of liquid fish glue.
7.Bring everything to the top right corner of the glass plate. Then bring a little of that quantity to the centre of the glass plate. Pour some distilled water on top and rub through the amount with the muller several times. Make a movement resembling an eight, do this several times.
8.Each time, clean the edges of the muller with a palette knife and add it back to the substance. When the gesso stops crackling while rubbing, scrape it together and bring it to the upper left corner of the glass plate with the palette knife.
9.Repeat each time with a little gesso and with a little water until you have had everything. Finally, transfer the gesso from the top left to the centre of the glass muller with the palette knife. Again add some water and rub a few times with the glass muller and then use the palette knife to heap everything together. By now it has become a smooth amount.
10. Now apply the gesso to a cardboard with baking paper, making as many round shapes as possible.
11.Let the gesso dry for a day and then make small grooves in the mass with a knife.
12. When the gesso has dried well, we can detach them from the baking paper. We can now break the rounds into small pieces .
13. We now put the pieces in a jar and can store the gesso for years. All we need to do when using it is to moisten it again until soft.
14. It is useful to label the bottom with the contents. This is especially important if you are going to make several of your own variations.
15. For re-using gesso, I use an egg cup. I put a few small pieces in there and mix them with clarified egg white. We let it become a soft mass and then gently stir it with a finger. Watch out for bits and for air bubbles. The latter used to be prevented by adding some earwax. Now we can also use clove oil. Note on: very, very little!
- Next, we apply the gesso with a brush or pen.
More on gesso and its use next time.
(*) Red earth from Armenia, oily and reddish in colour.