Chemical Formula

Question

​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

Brian Baade · Answer

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 conjugateddienes, which then undergoDiels-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).