Polymerized Tung Oil Finish
For a finish, I used Sutherland Welles Botanical Polymerized Tung Oil. Tung oil comes from the nuts of the tung tree (Vernicia fordii), which is native to southern China, northern Vietnam, and Burma. Pure tung oil, like linseed and other oils, takes a long time to dry, but with multiple coats it provides a fairly hard, water-resistant finish (some sources say waterproof but that’s pretty much impossible).
The drying time and other properties can be improved by polymerizing the oil via heat and chemicals; these are the same methods used to produce “boiled” linseed oil. Most of these finishes include metallic driers, petroleum solvents, and other toxic additives. Sutherland Welles says after years of research they have found driers with the lowest toxicity available and use as little as possible, relying on a more thorough cooking process. Additionally, their Botanical line uses a citrus-based solvent they call Di-Citrusol. D-Limonene (a more general name for this citrus derivative) comes from the oil extracted from citrus rinds, and has a variety of commercial uses. For example, the intense orange fragrance combined with solvent properties make it a common ingredient in cleaning products.
Note that “tung oil” has become a generic term like varnish; most finishes sold today as tung oil contain very little or no actual tung oil at all.
Polymerized Tung Oil Finishing Process
Oil finishes are not for people in a hurry. Even the polymerized versions take days of applying coats and waiting for them to dry. For the most part, I followed the directions given by Sutherland Welles. Where I cut corners is obvious to me upon close inspection, as the finish just does not look as good. I also had to contend with less than ideal environmental conditions, as my basement humidity was higher than the recommended maximum 65%.
I started with their Polymerized Tung Oil Sealer, which is probably about a 50/50 mix of polymerized tung oil and Di-Citrusol. The directions say to wipe on a coat, wait 10–15 minutes, wipe off the excess with a clean rag, then wait 6–8 hours to cure. Because of the higher humidity in my basement shop, I waited overnight. Following the directions, I then applied a second coat of sealer and allowed it to dry. I used #0000 steel wool to lightly sand the surface, then cleaned with denatured alcohol on a clean rag.
After two coats of sealer, I started to apply the primary finish coats, using their High Lustre Polymerized Tung Oil. (Note that “high” lustre is relative, an oil finish like this will never be as glossy as a film finish like shellac or polyurethane.) The directions are basically the same, except they say to wait 24 hours before applying another coat. Again, because of the higher humidity, I usually had to wait two days between coats.
It did not seem practical to me to try to finish the workbench fully assembled, so I took everything apart, and finished a few parts at a time. This extended the total finishing time, as I had four “batches” of parts to finish, each set taking several days. Partially because of how long it was taking, I only applied two coats of finish over the two coats of sealer; typically people build up three or four finish coats, sometimes more. I figured four coats total (sealer and finish) was enough for a workbench, and anyway I can apply more coats down the road without stripping and sanding what’s left of the existing coats.
The first coat takes more than subsequent ones as it soaks into the bare wood. So not surprisingly, I ended up using more of the sealer than the finish. I bought a quart of each, and as you can see in the photo, there is less sealer remaining. Still, considering the size of the workbench, there is plenty left for future projects.
Beeswax Finish
The directions for the wooden vise screws recommended finishing the handles, but not the threaded portions, then applying some kind of paste wax to both. I used beeswax, which has been used for centuries as a film finish. The beeswax cake was too hard to rub on as-is, so I put it in a glass jar and added some Di-Citrusol solvent to soften it into a paste which could be applied with a rag. After it dried, vigorous hand buffing removed the stickiness and left a smooth, slick surface. I also applied beeswax to the top of the front stretcher where the sliding vise moves back and forth.
Lower Shelf