GellerDemo3-05

Al Geller's club demo - March 19, 2005 - text by Ira Goldberg from Al's notes

Finishing, Design and Foil -
Al Geller’s talk on finishing and foils covered a lot of territory that is rarely addressed. He started talking about design, then sanding, next, on-lathe finishing, and finally the use of foils to accentuate turning. He commented, that approximately ¼ of his time is spent on each of design, turning, sanding, and finishing.

Design: Al presented three major points.
• First, design for the intended application. There are no “rules” but some guidelines are: for a decorative piece, make thin walls at the top and a little heavier at the base and turn the base to about ¼ to ⅓ of the maximum diameter of the piece. For a utilitarian piece, turn the base to ½ to ⅔ of the maximum diameter to give stability. In general, a recessed base is more attractive than a straight base because if gives “lift” to the piece.
• Second, examine the wood. Try to accentuate special features of the wood, and try to avoid straight elements. Avoid having the largest diameter at mid height.
• Third, in your design, draw variations to see how the features are best emphasized, then make an inside and an outside template that you can use during turning. This helps control the overall shape and the wall thickness.

Sanding: Al provided a handout from Fine Woodworking that compared American (CAMI) and European (FEPA) grades of sandpaper. The FEPA grades are designated with a P before the grit. The average grain sizes in both grades are similar for grades coarser than 180 or 220 grit. However, for finer grades, the same number in the CAMI system is finer than in the FEPA system. [Writer’s note: the range of grain sizes for the same average grain size is broader in the CAMI system than the FEPA system. This may or may not be an advantage. It is less likely to get larger grains and therefore large scratches using FEPA paper, but the scratches produced by FEPA graded paper are more consistent and sometimes more visible.]
• When sanding on the lathe, use 100-200 rpm or as low a speed as possible. At low speeds, there is less bouncing so the entire surface is sanded, there is less heating which causes burning or delamination, and there is less chance of heating and thus cracking wet wood.
• Placing disks on foam pads for sanding ensures that the paper contours to the shape of the turned piece. Generally he uses cloth-backed disks with Velcro to attach to sanding arbors. Stiff (paper) disks don’t work well, and tend to heat and delaminate from the Velcro backing. Diameters of disks should be about ¼ to ½” oversize to sand the edges (Al cuts his own discs from square sheets to achieve this oversize dimension). Al’s preferences are padded or cloth backed papers such as “Rhyno Grit” from Industrial Abrasives, or from Packard.
• Be sure to use all grades, i.e. start with the coarsest grit needed and then don’t skip grits as you sand finer. The final grade depends on the type of wood and can be anywhere between 220 and 2000 grit. Hard [close-grained] woods need a higher grit. Al typically sands to 600 grit on most woods and finer grit on very hard wood or synthetic material. It is possible to burnish the wood if the lathe is turning too fast or the grit is too fine and this may either help show up scratches that need to be sanded out or hide them if the grain is smashed down.
• Test the surface with water, lacquer thinner or acetone to visualize scratches. Water will also raise the grain. Stop the lathe and hand sand or power sand rough or torn-grain areas.

Finishes: Al talked about different kinds of finish. He placed them in three categories: (1)Oil and Wax, (2)wipe on and wipe off, (3)and spray on.
• A typical oil and wax finish is two coats of mineral oil [writer’s note: mineral oil and paraffin oil are the same] and one coat of wax. Mineral oil does not turn the wood to an amber color. Alternatives to mineral oil are walnut oil or linseed oil.
• Two wipe-on wipe-off finishes that Al uses are Profin™ and Waterlox™. There are many other similar commercial products made by Minwax™ and Watco™, etc. These cure in air, and should be put in small containers after they are opened or protected with Bloxygen™. Al notes that while Profin™ is difficult to clean from hands and surfaces it is his favorite finish. These are fool-proof finishes and are easy to apply. After the finish cures coat with any kind of wax. Be sure to dispose of rags properly because they support spontaneous combustion.
• A wide variety of spray-on finishes are available, including shellac, acrylic varnish, and nitrocellulose lacquer. Some yellow the wood more than others. Shellac is one of his favorites, and it can be sprayed or brushed. Streaks can be eliminated by wiping with a rag moistened with denatured alcohol.
• Lacquers are the most difficult to apply. They can be sprayed or wiped on, but are brittle and don’t build well. Generally use at least five coats, and use 0000-grade steel wool between coats.
Foils: As the final part of the presentation, Al demonstrated application of foils or “gold leaf.” The sequence is as follows:
• All surfaces, brushes and hands must be clean. The wood must be smooth. Any raised grain, tear-out or dust will show through the foil. [Author’s note: gold leaf thickness is 0.000005” to 0.0000065”, and thicknesses of other foils can be up to 0.000015”.]
• Seal the surface completely – the surface finish will come through the foil. Sand the sealer smooth. Mask areas that you do not want coated with foil.
• Lay out the foil so you know how you are going to apply it.
• Apply a thin coat of size [adhesive]. Brush out all bumps to get a smooth surface. Spray on size is also available.
• After the size dries it is tacky. It is better to wait than to rush application.
• Carefully lay the foil and brush from the center to the ends, or start with an edge and brush to the opposite edge. Add pieces where the foil tears. Use a soft artists brush.
• When complete, let the size cure for about 24 hours.
• Seal the surface with a finish coat after the size is cured.
The NEI group (www.EasyLeaf.com) graciously donated several hundred dollars of materials to Channel Islands Woodturners for Al’s demonstration and for him to give samples to us to practice with. Please acknowledge Larry Neuberg and NEI for their generosity (see below under references).
References:
S. Purdy, “Making Sense of Sandpaper,” Fine Woodworking, July August 1997, pp. 632-667.
M. Schofield, “True Grit,” Fine Woodworking, March/April 2005, pp. 63-64.
B. Flexner, “Demystifying Wax,” Fine Woodworking, date not given.
D. Hogan, “Finishing turned Work – What I Do,” GWG Technical Tips -Dan Hogan on Finishing http://www.woodturners.org/tech_tips/finishing_dan_hogan.htm
Easy Leaf Products: 2005 Price and Product Catalog. NEI Group. 60001 Santa Monica Blvd., Los Angeles, CA 90038. 800-569-5323. www.EasyLeaf.com . E-mail, info@EasyLeaf.com.

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