The Mahoney Music Collection in the Archives and Special Collections contains wonderful books related to violin construction, which include but are not restricted to books about varnishes and woods. Below is just a sample.
Hammerl, Josef, Reiner Hammerl and Jess Nierenberg. Violin varnishes: interesting information on resins and basic materials for violin varnish and advice on varnishing. W. Germany: Josef u. Reiner Hammerl, [1988?]. ML845 .G3413 1988
Brough, J. C. S. Staining and polishing, including varnishing & other methods of finishing wood: with a complete index of fifteen hundred references. Philadelphia: Lippincott, . TT325 .B76 1918
Robinson, John Stuart. The Guarneri mold and modern violin making. Oklahoma City, OK: J.S. Robinson, c1982. ML802 .R62 1982
Vettori, Carlo. I quartetti della liuteria italiana: the quartets of Italian violin making. Firenze, Italy: 2006. ML750. V47 2006
Hough, Romeyn Beck. Hough’s encyclopaedia of American woods. 8 volumes and 3 sample books. New York: R. Speller, 1957-1979. SD536 .H832