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Question asked 2019-09-12 20:51:48 ...
Most recent comment 2019-09-12 21:37:10
Drying Oils
Paint Mediums
Solvents and Thinners
Dear Mitra Conservators,
I would like to know the chemical formula of linseed oil, stand oil, distilled turpentine, spike oil, and dammar varnish but I have found it difficult to find this information. Can someone provide this information for me or recommend a source ?
Best regards and thank you for the service your provide to artists,
Hector Hernandez
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Moderator Answer
(brian baade)
The question you posit is very slightly complicated by the
fact that as these are natural products; for the most part, the “formula” will
vary slightly. The Organic Chemistry of Museum Objects by Mills and White is a good reference for
this info. On the other hand, much of this is in no way proprietary and is
available on such egalitarian sources as WIKIPEDIA, where I copied much of the
following:
linseed oil
https://en.wikipedia.org/wiki/Linseed_oil
Stand Oil
Today this indicates linseed oil polymerized but not
oxidized by heating in the absence of oxygen. (see our downloadable pdf’s for
most of this info)
https://www.artcons.udel.edu/mitra/Documents/MITRA_Mediums_and_Additives.pdf
from Wikipedia”
Stand oil is generated by heating linseed oil near
300 °C for a few days in the complete absence of air. Under these
conditions, the polyunsaturated fatty esters convert to conjugated dienes, which then
undergo Diels-Alder reactions, leading to
crosslinking. The product, which is highly viscous, gives highly uniform
coatings that "dry" to more elastic coatings than linseed oil itself.
Soybean
oil can be treated similarly, but converts more slowly. On the other hand, tung oil
converts very quickly, being complete in minutes at 260 °C. Coatings
prepared from stand oils are less prone to yellowing than are coatings derived
from the parent oils.[18]
Do a search here on MITRA for earlier definitions of Stand
Oil which differ greatly from this definition.
Distilled turpentine
https://en.wikipedia.org/wiki/Turpentine
https://www.artcons.udel.edu/mitra/Documents/Solvents-and-Diluents.pdf
Spike oil
https://www.artcons.udel.edu/mitra/Documents/Solvents-and-Diluents.pdf
We do not have a specific chemical formula for Spike Oil on
hand but I am sure that I can find one soon and will post it here when I do.
Dammar
https://www.artcons.udel.edu/mitra/Documents/MITRA_Varnishes.pdf
Similarly, I will post this when I get a moment.
Finally, each manufacturer, if they still offer the more
archaic materials like dammar and spike oil, may have small additions of other
materials that they will not list in their ingredients (eg, in the past some
providers of dammar varnish would add small amounts of alcohol to their varnish
to precipitate out the waxy component and yield a clearer solution).
EditDelete
Moderator Answer
(brian baade)
This article mentions the mixtures in spike oil
https://www.tandfonline.com/doi/abs/10.1080/10412905.2004.9698698
EditDelete
Moderator Answer
(brian baade)
Dammar or Damar can refer to more than one resin although today it generally
is used to describe a particular resin. See
https://en.wikipedia.org/wiki/Dammar_gum
The following very complicated scientific paper describes the components of
their sample of dammar
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=14&ved=2ahUKEwjq7-bL2szkAhVQtlkKHeFpAsgQFjANegQICBAC&url=http%3A%2F%2Fwww.akademiabaru.com%2Fwvcarmea%2Fdocu%2F107.pdf&usg=AOvVaw2R7pzDa7QcwRlE98wTlxt5
Here is a far more succinct description of the chemical makeup of what is
generally called dammar resin
https://pubs.acs.org/doi/full/10.1021/acs.jnatprod.5b00916?src=recsys
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