it is a violin varnish apparently as used by stradavarius. propolis is said to do something with uv light, IIRC.
without re-reading it, part of the article i saw is below:
quote
PROPOLIS SOAP – Used as a Ground for Violin Varnish
by William Fulton
To introduce the subject of the ground I use under violin varnish let me present the following background:
In 1989 I attended the Tiverton Violin Conference in England and heard a presentation by Claire Barlow. It concerned the results of an investigation she had conducted on the ground that was used by the classical makers. She revealed that the ground appeared to contain something she described as “rubble.” Claire was unable to identify what the material was, but she did say, with some certainty, what it was not. Then in 1993 I attended a joint meeting of the Violin Society of America and the Catgut Acoustical Society and heard a presentation by Andrew Dipper where he discussed a mineral ground that he and Geary Baese were investigating in an attempt to reconstruct what Claire Barlow had discovered. That is the background now for my ideas on this mysterious ground.
I believe this ground was based on propolis, a byproduct of the beekeeping industry.
Back in the days of the old master violin makers, 1550–1730, people who kept bees didn't have the hives we have today. They kept their bees in skeps, baskets woven of straw. Each year, in preparation for the honey run, the beekeeper would clean the hive by leaching it in lye, the result of leaching wood ashes with water. (Today we scrape the propolis from the hive.) The lye would digest the propolis making the hive ready for the bees. This digesting process created a liquid soap from the propolis. It is my belief that this liquid soap was the source of the mysterious ground the violin makers used as an undercoat. (It was also probably used by artists of the time to make a smooth, sealed surface for paintings). Someone, be it the violin maker, artist, or perhaps a person who was engaged in dying cloth (it gives a beautiful gold color), would add alum (other metal salts can be used) to the lye-propolis mixture, precipitating an aluminum propolis soap. The resulting very bright yellow material, when washed, would be a very fine slurry ready to use as a ground.
How did the violin makers use this propolis soap? Here are my thoughts. The violin makers would scrape the surfaces of the violin smooth with scrapers. (You don't have to worry about the small imperfections caused by the curl of the maple picking out or small imperfections such as tool marks, etc., because they will be filled.) Then the wet slurry would be rubbed into the wood leaving a coating of this bright yellow soap on the surface. It is allowed to thoroughly dry and then it is rubbed, with the hand, to a very smooth, almost silk-like, surface. The material will fill all tool marks, all imperfections, gaps in the purfling, but the grain of the wood will be completely hidden. Next, a coating of clear varnish is applied and, if the index of refraction of the varnish is correct, the wood grain suddenly appears and the propolis soap will disappear. When dry, if there are any imperfections in the surface they are repaired by rubbing with more propolis soap and sealing with more varnish. This is continued until the surface is acceptable. Then more varnish is applied, a color glaze, and the instrument is finished.
This bright yellow aluminum soap actually seals the surface of the wood. The varnish is absorbed by the material but the varnish does not penetrate into the wood. When it is applied to the scraped surface, the top appears like corduroy, but the material fills the grooves of the corduroy, and the surface becomes smooth. After varnishing the growth lines in the top are accentuated, look darker, due to varnish being absorbed by the propolis soap.
Originally, when the skeps were leached in the lye, some organic matter other than the propolis was digested, such as dead bees, beeswax, etc. This gives a greenish-yellow color to the aluminum precipitate. To get a bright yellow color the liquid soap was allowed to stand until the organic matter formed a scum on top which was subsequently removed (It actually rots to form the scum.). Then a bright yellow color is produced when the alum is added. Of course today we do it differently but the results are the same.
The reason I believe this to be the ground is because it is, first of all, a very bright yellow, the color seen under most old varnishes, and, second, it is a product that was readily available to the violin maker. end quote
source
http://www.scavm.com/Fulton.htm
phil,
i should add that i only really looked at this because it seemed a shame to throw the stuff away!