I came across a facebook page about pre C20th painting. The woman who does it is not bad, but some of her practices are quite dangerous. I suggested she take a different approach and she asked for documentation. Which is fair enough. I just can't find it and I know I had it.
And looking through the internet... well, I won't be surprised if I have nightmares. The amount of misinformation, and dangerous misinformation at that, is just breathtaking.
The issue is gesso. That's a plaster-based treatment for panels for painting and gilding. There is a whole process to making the gesso, both grosso and sottile, and it was well-documented on the page in question, and well carried out. The gesso made had lead white in it, which is highly toxic but gives a superior result as it makes the gesso more durable and flexible (you can't bend it, it will crack, which is why you don't put it on canvas, but it is definitely less fragile with the lead white, and hardens better).
You have to use a well dried wood panel for gesso. Not kiln dried, but properly cured. It has to be sanded to a very smooth finish. And then coated with a size. Rabbit skin glue is usual. You treat both sides of the panel. Then you can apply the gesso. Thin coats are the order of the day, and again you apply to both sides, to minimise warping. You let it dry. You can scrape it with a flat blade to get off any little lumps, but if you have done your job well it shouldn't need too much. Then the fun begins.
Polishing.
Start with a damp piece of linen and use circular motions. The trick is to have the linen damp enough to be effective, but not so damp that it dissolves the gesso, and not so dry that it leaves marks. And don't be heavy handed. And take your time. I know that sounds like a palaver, but it is quite meditative. And when that is all finished you can burnish it with silver. I use an old spoon. It comes up a treat. You end up, if you have done it all correctly, with a surface that is perfectly smooth, with an egg-shell-like finish.
But Cennino Cennini, in "Il Libro dell'Arte", written some time before 1440, writes about smoothing out the initial coat of Gesso Grosso with the palm of your hand. This is a lead gesso he is talking about. He also writes of stirring the Gesso Sottile with your hand, as if making pancake batter.
Lead is very toxic. Lead poisoning causes, amongst other things, brain damage, vomiting, abdominal pain and eventually death. You can breathe it in (remember leaded petrol? The fumes were why we don't have it anymore), you can ingest it, and you can absorb it through your skin. Skin is porous. Cennini wasn't doing anyone any favours. (Although if you want documentation for gesso methods and recipes, he's the go to man. Keeps it simple, doesn't add crap. His system works. Just don't touch the stuff with bare skin. There's a good translation here. You want Section 6).
Okay, in his time the dangers weren't really understood. But they sure as hell are understood now and so we really should be modifying our practice.
This poor woman on facebook smoothed the top layer of her gesso sottile with her palm. Cennini actually says you shouldn't use your hand beyond the initial layer of a gesso grosso application (and believe me, I really wouldn't even do that. I like the idea of living and having my mind functioning). She got a nice finish, but I worry at what cost. Her palm and fingers were white. Particles have entered her system. Hopefully not too much.
Once your gesso is smooth and dry and hard you either paint directly on it, if you are using tempera, or you seal it with gelatine if you are using oil paints. Gesso is very absorbent. If you don't seal it, it sucks the oil out of your paint film. Not a good thing.
So I need to find the documentary evidence for the silver burnishing. And I can't. There are pages missing from my files. They may have gone in the house move nine years ago for all I know. It hadn't bothered me before because I know what to do. I should have been more careful. I'll keep looking.
Some of the rubbish I found on the internet while trying to find an online source included coating your panel with oil before sizing, adding a layer of resin after each layer of gesso (the gesso needs to be damp so that each layer adheres to the previous. Putting resin between these layers is mad), sealing the top layer with resin (that will yellow really badly, really quickly), and using acrylic gesso, which repels oil paint and tempera, so that's useless. Oh, and applying a thick layer of oil to the final layer. The moron who suggested that said it should be "impasto" which is impossible with oil. But time and again I came across the hand-smoothing thing. It makes me shudder.
The problem with the internet is anyone can publish anything. They don't need to know what they are doing, and many don't. When it comes to painting, the level of ignorance is apalling. And it gets shared and shared and shared. because we want to believe that if it is published it must be true. And it is not limited to the internet. A lot of the really bad stuff comes from a handful of books published in the 1980s which are based on poorly understood C19th academic practice (which had its own problems). And there are teachers out there who are spreading the same misinformation to their students, who trust them to know what is right and what is safe.
The misinformation annoys me. The dangerous misinformation scares me. So I suppose this is my little contribution - a vague hope that someone researching gesso with lead white might one day find this and think "maybe I shouldn't use my hand after all". That's why I am boring you all silly.
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| from Ars Bene Moriendi, France, 1470-1480 |
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