Tuesday, May 10, 2016

Venetian turpentine and boiled linseed

The strange brewing of substances for sticking wool to silk continues.  I am trying to use the recipes from the De Kethan Treatise/Sloane manuscript 345 as those are specifically described as being used for printing fabrics. They are called "assays" in the manuscript which is encouraging as "assays: are a term otherwise used as a preparatory layer for gilding with leaf metal. It certainly sounds promising and like the sort of thing I should be using. It also has the advantage of being a later manuscript, dated to the late 15th century and therefore relatively close to the time period I am aiming for. The recipe I am planning to use is a combination of boiled linseed oil, amber and colophony. Colophony is also called Greek Pitch and is a resin. The most easily accessible source of it modernly is bow rosin. I played violin all the way through college. I can tell you that there are few things quite as sticky as this stuff. It can also be found in soaps, shoe waxes, and glues.

The recipe: ‘Substancie tmaken daer alle verue in dinet Recipe .j. lb. Lyn olijs ende sidet een vre ende dan nemt (fol 25r) .viij. loet bernsteen ghepuluert, ende doen dy yn een erden poot ende ghiten dar op lyn olij dy voer gesoden is dat dy wynsteyn bedowen ys myt den olij ende laten dat syen en also langhe dat di bernsteen ghesmonten ys ende roret weel omme myt eyn yseren leppel. Ende als gesmouten ys dy bernsteen soe salment syghen doer een doeck ende doent totten irsten olij ende latent siden, ende pruuet op eyn leye of het sterck genoch sy Ende ist sterck genoch soe doet dar .4. (of 1)pontspigel hars yn ende latent syden een luttel ende dan so settet af, ende dan ys bereyt. 

from Braekman, W. L. Medische en technische Middelnederlandse recepten. Secretariaat van de Koninklijke academie voor Nederlandse Taal- en Letterkunde, Gent, 1975

‘To make substance that serves all paints Collect 1 pound of linseed oil and cook it for one hour. Then take (fol 25r) 8 lot pulverized amber, and put it in a clay pot and pour on it linseed oil that has been cooked so the amber is covered with the oil and leave it to cook until the amber is melted and stir it well with an iron spoon. And when the amber is melted one should sieve it through a piece of cloth and put it with the first oil and leave it to cook, and try on a piece of slate if it is strong enough. And when it is strong enough add 4 (or 1) pound of colophony and leave it to cook a little and then put it off (the fire), and then it is prepared’

Translation by Indra Kneepens in her thesis "Understanding historical recipes for the modification of linseed oil: an experimental study into the properties of modified linseed oil for use as binding media in early northern European panel painting."

In addition to having been mentioned as an ink for printing fabric, and discussion that it tended to be so viscous that it had to be thinned to use to paint with, and it being from the right ballpark time, Ms Kneepens also did extensive experimentation with this oil as part of her thesis. So, I decided that this was the oil for me to try on my crazy experiment. The only issue at all is the expense. Amber-colophony varnish is commercially available at $144 plus shipping for 30 ml. OUCH. Buying amber to burn and make my own is also a bit costly for an experiment, but i am currently shopping around.

I do have some other things going as other options though. I started some glovers size with leather scraps from the leather jerkin and ordered some Venetian turpentine. There was specific mention in the discussion of the 17th century flocked wall papers that the glue used for the flocking was ant-pest because it contained turpentine. I wondered about this a lot since turpentine is used for things like cleaning brushes and thinning paints and I wondered how that worked. Then I found Venetian turpentine. http://www.dickblick.com/products/sennelier-venice-turpentine/ It is a resin made from larch trees with the consistency of honey, a gluey sticky substance that was added to paint to create enamel like effects. Many of the linseed oil varnish mentioned in the various manuscripts from the 9th through the 16th century have boiled linseed combined with different resins. There's copal and incense and other evergreen saps. The Venetian turpentine is not only similar/exactly one of the resins used, it is easily obtainable from art suppliers (and not $144 per 30 ml.) Sounds like a winner to me. I'm not sure if the liquid resin will be any different than the colophony I'm trying, but figured a few options and trials were a good thing.

So grinding and straining and mixing continues as I prep to smear my silk with oil-- an action that seems totally wrong to me. Here's hoping it goes well.

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