Excuse me, Medievals. We made some gesso! #medievaltwitter #heritagecrafts #medievalmanuscripts #catsoftwitter 
Gesso is the sticky stuff that medieval illuminators used to attach the gold leaf to the parchment. Originally, egg glair or gum arabic was used, which was fine, but very flat. By 13th C, a new chalky mixture was used, raising the gold off the page (BL, Royal MS 1 D X, fol. 3v)
In these images, you can see where gesso has been applied but no gold leaf (fol. 54v), and also where the gold leaf has flaked off to reveal the gesso underneath (fol. 30v) - BL, Add MS 42555 bl.uk/manuscripts/Vi…
There are lots of recipes online, but are all basically the same. As always, I rely heavily on the excellent @LovettPatricia patricialovett.com/books/. This Youtube video is also very good
First, the preparing of the ingredients. Slaked plaster of Paris was the first thing. I got some from @cornelissen1855, but I didn’t know if it was slaked or not. But you can do a fun experiment with pH paper to see if it is. If the pH is green, it is slaked.
You also need egg glair. Whisk two egg whites until they are meringue-tastic. Cover and leave overnight, then scoop off the bubbly top stuff. The egg glair can be stored in a container for as long as you need it. (Although I am slightly concerned they look like urine samples)
Now the fun part - mixing everything together. Eight parts plaster of Paris, one part sugar, one part fish glue (seccotine), one part egg glair, a few drops gum arabic. A pinch of Armenian bole. Plus some distilled water. Lots of mortar and pestle action.
Chloe comes to inspect.
Luna chose to abandon the experiment to concentrate on her hunting skills.
Chloe did NOT like the fish glue.
It goes the colour of Elastoplast. The red bole is added partly to make it easier to see where you are applying the gesso, but also because it gives a warmer background if the gold doesn’t stick everywhere, or wears off later (BL, Arundel MS 68, fol. 166v)
But seemed very smooth - you don’t want any bits of grit in the gesso. It seemed quite gloopy still, and needed to be fluid enough to be painted on with a paintbrush. I added some distilled water, which worked, but unfortunately introduced a lot of bubbles
This is not good - this won’t give an even surface for the gold. But there is a trick to dispel the bubbles - oil of cloves. I love that with these recipes all these problems have been encountered before, and often there is a solution. And the cloves make it smell very seasonal
Uh-oh, gesso on the jeans. It washed out fine though (unlike the iron gall ink from a previous experiment). I wanted to know if it would actually work with the gold leaf, so I painted some of the fresh gesso onto some vellum and left it to dry overnight.
There was a lot of mixture, but you can dehydrate the gesso and use later. Drop dots onto foil, greaseproof paper, or acetate, wait for it to dry and then store in an airtight container. To rehydrate add distilled water or egg glair until you have the right consistency.
Next day - I breathed on the gesso to activate the adhesive and pressed the gold leaf over it. Using an agate burnisher, I rubbed on gold leaf using some glassine paper. And - it stuck! Hurrah! It did what it was supposed to. I’m ALWAYS amazed when it does what its supposed to do
But I’m not trying to do this perfectly. I’m just really interested in understanding the preparation medieval scribes would have used, before ink or gesso is put to parchment. And it's hard getting it right! (Cologny, Fondation Martin Bodmer, Cod. Bodmer 127, fol. 244r)
Still - I’m pretty pleased with the initial I did using the gesso, even if is a bit bumpy. This is from the Eadwine Psalter, fol. 10r bit.ly/2CBtjDH . If you want to watch an expert in action, watch Patricia Lovett youtube.com/watch?time_con…
She sit. She judge.
Just finishing the initial while Chloe entertains herself. The whole thing took about four days, as I waited overnight for the egg glair, then another for the gesso to dry, and another for the gold to settle before painting
So - that's it. If you already have the ingredients it takes about half hour to make, and you can store it. This wasn’t as much fun as the ink, but it gave a fabulous result and I will definitely be using this from now on. Bye for now! (MS. Bodley 764, fol. 51r)
Oh - if you like this kind of thing, I also did one for iron gall ink
Actually, sorry, I’ve just got a bit more to add. I also rehydrated the dried gesso to make sure that worked too
I dissolved six dots of gesso in a beaker with about six drops of distilled water and left it for about two/three hours. This time I used a quill to apply the gesso, which actually was much easier, and made me feel proper medieval!
I was really pleased by how smooth the gesso went on this time, and I even progressed to gilding with loose gold leaf, which was...challenging...but actually, extremely rewarding (apart from sneezing and gold dust billowing everywhere).
So - I think I am finished for now, thanks
So - I think I am finished for now, thanks
And here's a thread on cutting quills #medievalstuffwithcats
unroll @threadreaderapp
