From David Marks Studio
Answering Reader’s Questions
by David Marks
1. Preserving an Antique Finish: I bought this very old Chinese tray with half the lacquer worn off. I want to preserve what is left and use it to work on. Can I paint or spray some kind of clear finish on it? Barbara. David's Answer: Shellac is your best bet, as shellac will stick to almost anything and almost any finish will bond to shellac. You can purchase shellac flakes and mix your own 2 lb. cut with denatured alcohol, or the shellac by Bulls Eye works really well and is very convenient to use. The most important part of application is temperature and humidity conditions. Make sure you work with a scrap piece of wood and do some test samples before applying it to your antique Chinese tray. The ideal conditions would be a sunny day with temperatures around 75° to 80°. If it is a rainy or overcast day, then do not spray shellac—wait for a dryer day. Shellac can absorb moisture from the air on a day with high humidity levels, and the result will be a “milky” color to the finish. If you can spray it indoors in your studio, then make certain that the room/space has a thermometer in it, and it reads 75° or warmer for best results. When I work on an antique, I lightly clean the surface first and try to remove any wax that has been applied over the years. I used to use Naphtha, but it has been removed from California’s hardware and paint stores for health reasons. Old Asian lacquers are Urushi lacquers which are natural resins from their Sumac trees. Shellac is a natural resin harvested from the Lac bugs in India and other Asian countries. Even if you are not able to lightly clean the surface with a mild solvent, I believe the shellac will still bond to it. Cleaning the surface first is still your best option. Since Naphtha is no longer available, I would try some mineral spirits instead. Before using the mineral spirits, start by lightly brushing the surface with a soft dry paint brush to see if the old finish flakes off or is still intact. Once you have lightly brushed the surface and removed any dust or loose material from it, then take an old tee shirt or clean cotton cloth and moisten it with some paint thinner (you can purchase the odorless type which is more user friendly) and gently rub the surface. Do not use any abrasive material like steel wo ol or Scotch-Brite, it can remove some of the finish. Let the surface dry. It might look dull as a result, but it should be cleaner. Shellac flows best when it is warm. When I spray it as a solution I have mixed or from a can, I always try to warm it first. On a sunny day, simply leave the can in the sun until the can feels warm to your hands. I have an oil filled radiator in my finishing room, and I place the can on it until it feels really warm or you can just place the can next to a light bulb as a heat source. Shake the can really well, and use long, light, uniformly even strokes across the surface overlapping each stroke. The goal is to apply a light, wet, uniformly thin coat over the entire surface. The
Woodworker West July-August, 2013
David Marks has been a studio furniture maker in Santa Rosa, CA for nearly 40 years and was the host of the popular woodworking television program Wood Works on the DIY network. He also has been a contributor to Woodworker West, since 2004. Over seven seasons, David produced 91 episodes of WoodWorks, featuring step-by-step instructions for building contemporary studio furniture. He has recently secured a licensing agreement, re-edited them, and is making them available on his eStore: www.djmarks.com/ estore/. In addition to Season 1 and Season 2, Season 3 is now available, which can be purchased as a complete DVD of the full 13 episodes or episodes #301 thru #313 can be individually downloaded from the website. Also available are detailed production plans for each project from Seasons 1-4. David will be teaching the following hands-on classes at his studio in Santa Rosa, CA: Aug. 1-5 Finishing Aug. 16-18 Gilding & Chemical Patination Sept. 12-16 Intro to Wood Turning: Making Wooden Boxes Sept. 26-28 Intro to Bowl Turning Oct. 11-13 Curved Joinery Oct. 25-27 Marquetry & Inlay Nov. 9-11 Sharpening Scrapers/Handplanes Details on these and future classes at the David Marks Studio can be found at the website: www.djmarks.com/classes.asp. Page 36