Replacements for Nitric Acid in Varnish Making

[Marcus Bretto]

Hello all. So I've been reading up on as much information as I can within reason about the use of nitric acid in the cooking of varnish to produce color. Of course, reading about it has made me aware of the potential problems in using varnish produced with nitric acid. Some people claim to have success and others have many complaints from color shifts to drying problems to cracking and all sorts of fun stuff. Putting all of this aside, I have three main questions, both highly related. Does anyone know what quality of nitric acid produces the production of the colorant? Is it the oxidizing quality or the strength of the acid itself? Could the unnatural oxidation be what interferes with the drying time? Also, has anyone tried to achieve similar results with the use of chemical products other than nitric acid?

Edited February 10, 2018 by Marcus Bretto

[joerobson]

Have you read Charles Fry?  https://archive.org/stream/varnishesitalia00frygoog#page/n4/mode/2up

[Marcus Bretto]

On 2/11/2018 at 9:35 AM, joerobson said:

Have you read Charles Fry? https://archive.org/stream/varnishesitalia00frygoog#page/n4/mode/2up

Thank you for your response, Joe. I have had time to read portions of the Fry book since you're response. It certainly answers my question about drying times relating to oxidation, but I haven't seen any mention of his experimentation with other acids or oxidizers either in my reading or in a digital search of terms in the book. As far as I can see within my days of searching, there is no mention of anyone in the violin world branching out from using this acid, either. I have, however, found multiple scientific articles from the 1800 and 1900's demonstrating the use of other chemicals on resins and linseed oil, and a few of them seem promising in their results.

Edited February 13, 2018 by Marcus Bretto

[joerobson]

On 2/11/2018 at 11:59 PM, Marcus Bretto said:

Thank you for your response, Joe. I have had time to read portions of the Fry book since you're response. It certainly answers my question about drying times relating to oxidation, but I haven't seen any mention of his experimentation with other acids or oxidizers either in my reading or in a digital search of terms in the book. As far as I can see within my days of searching, there is no mention of anyone in the violin world branching out from using this acid, either. I have, however, found multiple scientific articles from the 1800 and 1900's demonstrating the use of other chemicals on resins and linseed oil, and a few of them seem promising in their results.

Resins are often altered using metal salts, particularly colophony, but generally not as oxidizers.