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Finish for turned bowls
I am a novice woodturner. When I finish making bowls I use either tung oil or walnut oil to finish the bowls. I'd like a better shine on the bowls and I was wondering if there was something I could use that is food safe or can I apply something to the finished bowls.
First, let’s look at the finishes you are already using and why you aren’t getting a shine. Walnut oil is a non-curing oil, meaning it stays in liquid form indefinitely. As a penetrating finish it works really well, but as you discovered; it doesn’t shine up easily.
Tung oil, on the other hand, is curing oil. Eventually pure Tung oil will harden to a film, and with multiple coats and very long cure times, it can be polished to a decent shine….but it’s not ideal. If you want to stick with oil finishes, you can buy Tung oil that is labeled as “polymerized” which will work better, as it has undergone a process and contains additives which cause it to cure faster and harder, but again; not ideal. One note with both of these finishes. Both Tung and Walnut oils are nut oils, and as you are using these bowls for food, there is a small risk of someone with nut allergies having a reaction to the finish.
As far as other finishes? There are a bunch that will work. If it’s a very shiny finish you are after, you are going to need to use a hard film-forming finish, as it accepts the best polish. Now in this category there are two ways you can go: Applied finishes such as polyurethane or varnish, or one of the available turner’s waxes or polishes.
Believe it or not, most polyurethanes, lacquers and varnishes are food safe *once cured*. Once the volatiles have evaporated, what’s left is actually a thin film of plastic and is safe to use for temporary food contact. If you are looking for a super-high gloss, one of these will be your best choice. The only downside is that these finishes can be hard to apply, especially on a lathe.
My #1 choice is to use a friction polish such as Shellawax. To get a shiny bowl, you would lathe sand your bowl up through the grits (I’ll usually stop at 1000 grit, some will go higher) and then apply the polish to the spinning bowl with a rag. The heat from the polishing process actually starts a chemical reaction that causes the finish to dry almost instantly, and the resulting finish has a deep shine.
Finally, as for making your existing bowls shinier; Assuming they are well sanded, the best approach is to apply a hard wax such as the Liberon turner’s Carnauba wax from Lee Valley and then high-speed buff to shine.
I hope this helps Dale,