Posted on March 4, 2024May 16, 2025 by Dale Phillips Chemical Stains Chemical Stains by Michael Darnton Originally published in American Lutherie #32, 1992 and Big Red Book of American Lutherie Volume Three, 2004 One of the biggest problems for the violin maker trying to replicate the effects of time is the imitation of the color of ancient wood. Even unantiqued instruments benefit from the rich appearance of old, time-darkened wood under a coat of fine varnish. Chemical stains have the greatest promise for replicating the look of old wood. Unlike aniline and pigment dyes which insert foreign colors into the wood, either in the form of a soluble dye or of a solid pigment, chemical stains cause a color change in the wood itself. The change is both permanent and clean-looking when compared to that of aniline and pigment colors. Become A Member to Continue Reading This Article This article is part of our premium web content offered to Guild members. To view this and other web articles, join the Guild of American Luthiers. Members also receive 4 annual issues of American Lutherie and get discounts on products. For details, visit the membership page. If you are already a member, login for access or contact us to setup your account.
Posted on August 1, 2022May 19, 2025 by Dale Phillips Potassium Dichromate, Oxalic Acid, and Carnauba Wax Potassium Dichromate, Oxalic Acid, and Carnauba Wax by Jeffrey R. Elliott Originally published in Guild of American Luthiers Data Sheet #52, and #55, 1977 and Big Red Book of American Lutherie, Volume One, 2000 Potassium dichromate. European luthiers commonly use potassium dichromate to give that nice, brown “aged” look to lighter, newer woods. It can be used by itself or mixed with aniline dyes for additional color tints. Primarily it has been used to darken the interiors of violin-family instruments, although I know of many who have used it on the exterior to darken spruce and maple. I have used it both inside and out to create a “naturally aged” looking wood on guitars. Potassium dichromate is a chemical activated by light from the sun, sunlamp, or infrared lamp, but direct, natural, full-spectrum sunlight is best. Beware: Indirect light will not activate it, and the solution will tend to color the wood a murky green. The solution is rather weak — two tablespoons to one gallon of water. It can be applied by brushing or by wiping it on with a cloth (wear gloves). Although I have never tried it, I imagine a spray method would work as well. Whichever method is used, a light, even coat is recommended. Become A Member to Continue Reading This Article This article is part of our premium web content offered to Guild members. To view this and other web articles, join the Guild of American Luthiers. Members also receive 4 annual issues of American Lutherie and get discounts on products. For details, visit the membership page. If you are already a member, login for access or contact us to setup your account.
Posted on August 1, 2022May 20, 2025 by Dale Phillips Spray Gun Agitator Spray Gun Agitator by Jimmie Van Originally published in Guild of American Luthiers Data Sheet #91, 1978 A new product that I found to be most helpful when spraying a finish or other things that had to be in complete suspension to assure uniform coverage, is a agitator siphon cup assemble sold by N.A.P.A. auto part stores. This cup will work on most major brand guns. The 1 quart cup provides constant agitation from air right off of the same line that your gun works off of, no extra line is needed. You can control the mixing speeds of the agitator, and does not require an extra cleaning. The part number you need to ask for is model 70-707. This may be of big help to those of you who do a lot of finishing work. ◆
Posted on August 1, 2022May 20, 2025 by Dale Phillips Glass Jars for Spray Guns Glass Jars for Spray Guns by Tim Olsen Originally published in Guild of American Luthiers Data Sheet #91, 1978 Commercial spray guns, such as the DeVilbiss type MBC, typically use aluminum cans to hold the juice. Aluminum cans are lightweight and unbreakable. They are also expensive and inconvenient, in that they must be labeled; the contents can not be viewed without uncorking the cans. By substituting glass jars for the aluminum cans, many advantages can be realized: Jars are cheap. Jars are clear, allowing one to observe the contents instantly, and to check for sediments, precipitates, jungjills, farfles, and other forms of grungus. Become A Member to Continue Reading This Article This article is part of our premium web content offered to Guild members. To view this and other web articles, join the Guild of American Luthiers. Members also receive 4 annual issues of American Lutherie and get discounts on products. For details, visit the membership page. If you are already a member, login for access or contact us to setup your account.
Posted on August 1, 2022May 23, 2025 by Dale Phillips Questions: Tru-Oil Finishes Questions: Tru-Oil Finishes by Jeff Jewitt Originally published in American Lutherie #90, 2007 ■ Eric Nicholson of Northern Ireland asks: Woodworker magazine published an article on Stewart Adamson’s work regarding Tru-Oil finishes. His method involved a considerable amount of work with Micro-mesh during the process. I tried his method on my own guitars, both classical and steel string, with very satisfying results. Tru-Oil gives an attractive semigloss finish on all woods, but Adamson also goes on to say that for those that like a gloss finish, a gloss tung oil is now available only in the USA. Does anyone know of this gloss tung oil and where it is available in the States, or if it is now available in the UK? Jeff Jewett of Homestead Finishing in Cleveland Ohio responds: Tru-Oil is not pure tung oil. It’s a mixture of linseed oil, mineral spirits, and, according to the manufacturer, “modified oil.” It’s arguable that no tung oil is even used in this stuff. When finish chemists talk about “modified oil” as an ingredient they typically mean either chemical modification or heat modification. Chemically modifying a drying oil involves reacting it with chemicals and heat to form what are known as alkyds, which are used in varnish manufacture. Heat-treated oils basically jump start the drying/curing process. Pure heat-treated oils are used all the time in making finishes, but they rarely show up as “finishes.” The only pure heat-treated linseed oil I know of is Tried and True “Varnish Oil.” Pure heat-treated tung oil is sold in this country under the Sutherland Welles brand (www.sutherlandwelles.com). So I would be tempted to say that Tru-Oil is a mix of linseed oil and some sort of modified linseed or tung oil. Because it has a high oil content, it is not possible to produce a very glossy finish. High oil (also known as long oil) products tend to form microscopic wrinkles at the surface as they cure. There is one way to heat-modify pure tung oil so that it will form a glossy film. This involves careful and controlled heating of the oil to about 450°F. Very few people can cook tung oil properly nowadays, but you can buy it under the Sutherland Welles brand “Original Formula High Lustre.” I don’t know if they will ship overseas. It’s not an easy finish to do, and I’m not sure that it will match the gloss of a French polish, but at least you know it is real tung oil, along with solvent and some driers.
