Oil Varnish Techniques

by David Rolfe

Originally published as Guild of American Luthiers Data Sheet #89, 1978 and in Big Red Book of American Lutherie Volume One, 2000



I decided to investigate the use of traditional oil varnishes as used by violin makers. At first sight, there seemed to be a lot of information around with enough detail to get on with the job. But as I delved deeper, I found enormous gaps in details of technique and lack of information on what is important and what is not. This is a detailed summary of what I have learned so far. My basic sources of information are the books and articles listed at the end.

Materials

Varnish. Traditional oil varnishes consist of a variety of resins, heated and dissolved in linseed oil, and turpentine. Coloring is added, and these agents can either be from the heartwood of certain trees (like dragon’s blood or gamboge) or organic mineral salts. Linseed oil is a slow-drying oil, and in conjunction with the resins, goes through the process of oxidation and polymerization (molecules of short length combine to become longer). Polymerization occurs mainly in the presence of ultraviolet light and continues for decades. Turpentine is used as a thinner or as a solvent to get the varnish on and then to evaporate in a relatively short time. The important characteristics of the varnish in liquid form are: