What it is, and how to make your own.
What is Gesso?
Gesso is a ground used in art as a basis for painting and/or gold leafing. It is made up of a mixture of animal skin glue or hide glue dissolved in warm water to which is added marble dust or chalk and a white pigment, such as titanium dioxide. The marble dust is added to the rabbit skin glue mixture until it reaches the consistency of a heavy cream. When the mixture is ready, it is applied to a wooden board which has been cut and sanded to a smooth finish.
Oftentimes several coats of gesso are applied to the board. After one coat is brushed on, it is allowed to dry. When it is dry, it is lightly sanded with a very fine grade of sand paper, generally 220 or above. An additional coat of gesso can then be applied. It is up to the artist as to how many coats of gesso one wishes to place on the board. Although many people like to go with two or three coats, in traditional iconography, as many an ten coats are used. When the board is ready, it has the feel of a fine porcelain.
How to Make Gesso
To make your own gesso, you will need:
- a double boiler ~ this is a pot placed above another larger pot with water in it set to simmer. This is designed to keep the temperature in the the suspended pot at a consistent temperature without burning the ingredients.
- rabbit skin glue ~ or animal hide glue.
- marble dust ~ or special chalk, the one from the Champagne region in France is well known for its quality.
- white pigment ~ this is optional and can be added to the mixture should you wish a brighter surface ~ Powdered titanium dioxide is usually added.
The basic recipe is as follows:
- 1/4 cup Rabbit Skin Glue
- 2 and a half cups water
- Marble Dust (Generally about 2 and a half cups)
- White pigment
- Bristle brush
- Sand paper
In a double boiler, dissolve the rabbit skin glue. Keep an eye on the mixture so that it does not boil. If the glue were to boil it could compromise the integrity of the finished gesso. It is best to keep the heat at a medium to medium-high temperature.
When the glue is completely dissolved, slowly add the marble dust. To keep the mixture from clumping, it can be helpful to sift the marble dust in. When the marble dust reaches a level within 1/4 inch of the top of the double boiler insert, stir the mixture slowly with a wooden spoon. At this point you can decide whether or not you would like it a bit thicker. If you wish it to be thicker, you can add more marble dust.
Once the mixture is ready, you can apply it to your board using your bristle brush. Brush on a smooth layer of the gesso and let dry. Once it is dry, lightly sand that layer down and add another according to how many one desires.
This kind of traditional Gesso is not recommended for use on canvas as it could crack and become brittle.
To Store Extra Gesso
If you have extra gesso left over that you are not going to use right away, it can be stored for later use. Place the excess in a glass jar and allow to cool down and stiffen. When the gesso is hard, add a coating of isopropyl alcohol to a depth of about three-quarters of an inch. Store the mixture in the refrigerator to prevent it from going bad.
If left out, the hide glue can go bad resulting in a terrible odor and an unusable mixture.
To re-use, pour off the alcohol into a small glass or other receptacle. Take out the amount of gesso that you need. Should you not be using all of the gesso at this time, once you remove what you need, pour the alcohol back onto what is left in the jar and store, once again, in the refrigerator.