Gesso for the unversed
December 10, 2022 at 6:08 am
It seldom is enough to master only one's own craft.
In boneworking we often come in touch with the realm of basic metalworking [1], elements of colour technology [2], chemistry, and lots of miscellaneous, really weird stuff.
Experience has taught, that about once a year ''the cruel destiny'' also expects us to practice the noble art of painting on wood. In oil.
To anyone who has worked with oil colours, the most unerasable memories of this labor would surely be the torturous waiting for the oil to dry. And if you happen to paint on wood, weeks can go by, while layer upon layer, you satisfy the poor boards’ eternal thirst for more oil. It just sucks it in, never gives it back...
Well, unless you are smart! And, trust us, people in bygone eras really were smart.
There is this thing called gesso (from Italian), that traditionally is used as a ground colour (as a primer, if you like) in such cases. It is even claimed to shorten the drying time of the colour [3]. And traditionally, since nobody recalls when, this thing, the gesso, has been made by mixing hide glue, or such, with chalk [4].
But don’t be misled – it is way more tricky than it sounds! The mixture should be made exactly in the right proportions, made not too liquid, not too dense, applied in the right way, and thus often in the end this gesso will crack or surprise you and your friends and family in some other way [5].
This is then where our recipe – ‘’Gesso for the unversed’ - ’ comes in the limelight. Indeed it consists of lime, chalk, and cottage cheese. It is based on the cheese glue described by our friend Theophilus in the 12th century [6].
How it is done?
Roughly 20% weight fatless cottage cheese (or curd if you will) ( containing 0,1% or less fat and as much protein as possible).
About 5% weight of slaked lime (Ca(OH)₂).
Approximately 75% of chalk (about 5% of that can be substituted by another pigment, thus giving the possibility to pre–tone this gesso)
Then:
Add the slaked lime to the cottage cheese and mix it thoroughly in a mortar. Add a bit of water when the mass becomes too sticky. Mix the chalk with water. Add to this the mixture of cottage cheese and lime. Mix it nicely, add water as much as you want, but it works the best if it is rather thick than thin.
Apply.
Let it dry for at least a day.
This Gesso allows a large margin of mistake, one can safely measure the ingredients ‘’by eye’’. It won’t crack, is easy to work with. Use various layers if needed, you can apply the next layer almost as soon as you have finished painting the previous one.... It is simply gorgeous to work with and then to work on it.
In the picture: Our improvized backgammon board painted on wood, gesso - ed using our recipe Oil colour , pigments: titanium white, iron oxide red, iron oxide black. Colour has been applied in one thin layer. The finishing second layer is yet to come (the event came faster, as it often happens).
And our bone counters...
[4] For shorthand facts and fiction, consult : https://en.wikipedia.org/wiki/Gesso ; https://www.britannica.com/art/gesso
[6]Please consult: https://experimentingwiththemedieval.wordpress.com/...