Walnut, Shellac, and Surface Preparation
November 26, 2012 § 1 Comment
I’m in the home stretch of building a little walnut stool, adapted from those I saw at the Kam Wah Chung State Heritage Site in John Day, OR. I took some scrap walnut from the project and did a little experiment with finishing. I’ll be using shellac and I wanted to see if I could detect any differences in the finish depending on how the surface was prepared. One half of the scrap was planed with a smoothing plane. The other side was planed, though not to the level of gossamer shavings as from a finely set smoothing plane, and then sanded with 220-grit sandpaper wrapped around a cork block. At this point in the game there is obviously no contest between the two. The planed surface absolutely shines, and the sanded wood looks dull, muddy, and lifeless.
Next I tried to closely approximate how I foresee finishing the final piece. I padded on several coats of 1-pound cut amber shellac, and lightly sanded with 400-grit sandpaper after the first and last coats. Paste wax was then added as a final treatment. And in the end I could personally see no difference. When I asked Judy if she saw a difference, her response was the same, “Nope”. It’s almost impossible to show subtleties of finishes on a computer screen, but below is a picture of both sides finished (I didn’t get a good “before” picture so you’ll just have to trust me on that).
By no means am I going to stop using my smoothing plane, but this does quell some of my fears about having some surfaces on a piece planed, while others might be sanded or scraped to remove some tearout or other dings (I’ll still do everything I can to not power sand, however). At least under shellac, a smooth surface from either planing, scraping, or sanding will likely all look the same in the end. I have yet to experiment with oil and varnish to see if the same holds true.
Unfortunately we are in a bit of crisis when it comes to securing seedlac, the resin produced from brood lac bugs that comprises the raw ingredients for shellac. The last two years have yielded very low crop yields, and that has caused the price of shellac to increase dramatically. Habitat loss for the brood lac insect in its native India is one speculative cause, which could be bad news for the future because habitat loss can be very difficult to reverse.
The price of Zinsser pre-mixed shellac is also rising, and for some it remains more convenient than mixing it from scratch. If you want to make your own from flakes, two good sources are Shellac.net on the east coast and Shellac Shack on the west coast. Due to the low crop yields, BT&C flakes (which I’m using to finish my stool) are currently unavailable at Tools for Working Wood. Your local Woodcraft may still have some in stock.
Jeff Jewitt has great finishing information and products on his Homestead Finishing Products website, including lots of nice stuff on shellac.