2015 August Meeting WrapUp
TEW Finishing program, August 10, 2015 Wrap Up by Derek:
Our round-table discussion on finishing was very successful. Cleve, our vice president, skillfully guided the discussion through all the stages, from preparation to finishing to final polishing. He passed around Bob Flexner’s book, “Understanding Wood Finishing”, saying that it is an excellent reference. Taz started the discussion off, showing some computer graphs of the drying process of pieces turned green. His frequent weighings of the pieces showed that most moisture was released in twenty days, and moisture loss reached zero at around thirty days. This was for pieces that were finish-turned, of roughly 3/8” thickness. Taz also talked about soaking pieces in alcohol for a short time (~24 hours), at the start of the drying process. Dave Wahl and Alan mentioned boiling as a first step, with a similar goal of speeding drying and reducing drying distortion. Elliot outlined his use of the microwave oven to speed drying.
There was a lot of discussion about sanding. I learned that most people stop sanding at 400 grit or below, depending, of course, on the details of the piece, and the planned finish. Many members use Abranet abrasive mesh, which is excellent for clearing sawdust. The foam-backed Abralon was also widely used, especially to polish finishes in the higher grits. Bob Seigel spoke highly of another foam-backed abrasive, Gold-Flex. All of these products are made by the company Mirka. Cleve showed an example of the 3M Imperial abrasive film, which he had recently bought. Someone else asked about the ceramic-based abrasives. Antone, and others, said that they were good products, but not worth the high cost, in their experience. Dave mentioned sanding wet, either with oil, or with water as a lubricant. He said this reduces or eliminates the scratches that would be visible with the same grit used dry. I had heard of sanding with oil, but not about sanding wood with water. I plan to give it a try.
When the discussion turned to adding color, pigment stains didn’t seem to have much support. Ralph made a strong case for Procion MX dyes, sold for fabric dying. He said these dyes are the most colorfast available. Dave Wahl mentioned that he has had good luck with Rit fabric dyes, and David Burling shared positive experiences with Solar-Lux dyes. Several members recounted fading problems with alcohol-soluble dyes, and all agreed that Jimmy Clewes setting the dye and turning on fire was great showmanship, but not an essential step in adding color.
Wipe-on Polyurethane is a popular finish, which helps enhance the prominence and contrast of the grain. Alan lauded the gel variety. Poly helps “pop the grain,” emphasizing the attractive grain pattern on some woods. Cleve introduced the term “chatoyancy” to the discussion, with is used to describe the shimmering changes in light reflection that curly, fiddle-back, and other grain patterns exhibit. Oil is particularly effective for enhancing chatoyancy, and many members use oils such as linseed oil or tung oil, or the oil-varnish blends generically called “Danish oil”. Watco and Waterlox are two examples of Danish oil used by several members. Antone said he uses pure tung oil, and he, Alan, and Derek noted that many products labeled “tung oil” may contain little or no tung oil. Several members mentioned mixing their own blend of oil, varnish, and solvent, and Dave said that Sam Maloof’s finish is that sort of combination. Bob and some other members said they liked using walnut oil. Elliot cautioned that using oil on a spalted piece can be a disaster.
Alan explained that CA glue can be used as a base for finish, and it will enhance chatoyancy/pop the grain. He said that he uses it underneath several different finishes. It fills the grain, and gives the evenness and sheen that would take four or five coats of a solvent finish to attain. Alan said that CA is compatible under any other finish, and Floyd mentioned that he sometimes uses it as the only finishing material on some of his pens. Cleve mentioned that he had read that shellac can be used under any finish, and Derek said that this is true for de-waxed shellac, but that many shellac products contain wax, which might interfere with adhesion for some top coats. Derek recommended Zinsser’s SealCoat de-waxed shellac.
Alan said that he likes lacquer for a high-gloss finish, and this was seconded by several other members. He noted that traditional nitro-cellulose lacquer is hard to find these days, and that he prefers acrylic lacquer. Cleve endorsed Krylon acrylic lacquer. Derek said he likes shellac as a topcoat as well as a sealer. Several members mentioned friction polish. Cleve pointed out that there are multiple formulations sold as friction polish, including some that contain linseed oil and/or lacquer. Derek uses the Mylands product that contains shellac and wax. Ralph mentioned the possibility of using pure carnauba wax as a finish, and Bob suggested that on stabilized woods, he sometimes just buffs with white rouge.
That led us to polishing the finish and adding wax. Antone said that carnauba wax is the hardest wax derived from plants. Other options include synthetics and waxes derived from petroleum. Some microcrystalline waxes, such as Renaissance Wax, that are considered to be archival. He said that many of the finishing processes that we had discussed could not be considered archival, and if we wanted our finish to last as long as our turnings, passed on for 500 years, we would probably need to approach finishing differently. Alan, Dave, and Cleve mentioned automotive rubbing compounds and polishing materials as useful for getting a high polish on a finish. Ralph said he got as good a gloss from wipe-on poly as someone using a buffing system. Derek mentioned that he is currently experimenting with the Dr. Kirk’s line of polishing waxes from Craft Supplies. He reported mixed feelings, since the first product in the system, Scratch-Free, liquifies at summer air temperatures, and the final product, the microcrystalline Versa-Wax, is somewhat hard to apply.