I promised to write about Shellac and tung Oil after I finished my rack (the first one), so here it is. I should mention that this post is not about which finish is better as much as it is about my experience with each one.
I got the idea to finish my rack in tung oil from a friend who builds Dietz cabs out of baltic birch ply and uses tung oil to finish them. When I was looking into tung oil I learned that there are two kinds of tung oil. One kind is really a varnish, like Fromby’s tung oil, or any other kind of tung oil you can get at the hardware store. Then there’s real tung oil which is an actual oil, made from a nut, and needs to be cut with citrus solvent or it’ll never dry.
The varnish tung oil is fine, but it’s made of chemicals that are toxic, and if you can’t finish outside or in a well ventilated shop, then you really shouldn’t use it. That’s why I went for the real tung oil which is made of safe materials. The one I bought is made by Real Milk Paint, and I really recommend them if you’re looking for actual tung oil. You can call them and they actually answer the phone and answer whatever questions you might have. They recommend using citrus solvent to thin their oil, but being a cheapskate I thought maybe 99% isopropyl would work, and they were positive that it would. Honestly, I’m not sure it did. I think it did, because the oil seeped into the wood, but this was my first time using tung oil, so who knows.
I wasn’t happy with the way the finish turned out. I think some finishes and some woods don’t work well together, meaning that the finish brings unattractive colors out of the wood. That’s what happened with the tung oil and Baltic birch. The wood looked unnaturally yellow and orange, and the grain popped out but in a weird and unflattering way. This was a surprise because I tested the oil on a scrap piece and it looked find, but I guess I underestimated what it would look like on the whole thing. Here are a few before and after pictures.
As you can see, it’s orange and yellow and the edges look burnt. It doesn’t look as bad in the first three pictures with the oil on, but in the last one, which was taken under a lower light, it looks pretty bad, but even that is quite flattering. Notice the little shelf in the bottom of the last picture. It was made from the same slab of birch plywood, but it didn’t have as many layers of tung oil. I’d like to elaborate on that.
Fewer layers of tung oil will result in the piece looking less orange and yellow – just look at the rack vs. the shelf. The shelf looks better because it didn’t have as many applications of oil. It’s also important to keep in mind that tung oil is, well, an oil. This means that while it’ll protect (and seal, I think) the wood, you will still be able to feel the grain underneath. It’s not a clear, hard finish that comes between the wood and the environment, so think of what you’re making, its application, and whether or not tung oil would work for it. I wouldn’t hesitate to use tung oil on a cutting board, wood bowl, wooden spoon, etc. At the same time, a coat or two of tung oil could be nice to use under another finish just to give the wood a bit of a color and help the grain pop.
Keep in mind that tung oil has a really strong smell. It’s a nut-like smell, but it’s really strong and our apartment smelled like it for a while until I washed the floors a couple of times and kept airing out the place. It also helped when I moved the rack to the basement. My understanding is that the citrus solvent will work to counter the smell, so if you were to use tung oil on something that needs to be food safe, it’s a good idea to use citrus solvent. In fact, I’d use it anyway.
Kind of like tung oil, there’s the stuff you buy at the store or you can mix your own. The Zinsser product, which is available everyone, is fine. It’s a bit thick (I think it’s a 3lb cut), but worse they put a lot of stuff in it that’s harmful, so again it’s not a great idea to use Zinsser shellac inside and without ventilation. I actually got woozy from applying it at home even with the windows open. Then I read the GHS document for their shellac and god really scared, so I decided to get flakes and mix my own shellac. (I got my flakes from shellac.net).
Mixing shellac is very simple. You crush the flakes and mix them with alcohol. The ratio is determined by the kind of cut you want. The higher the shellac ratio, the thicker the solution will be. The solution should be kept in a plastic or glass container, but not metal. Most people use denatured alcohol, but since it’s toxic, I decided to look into 99% isopropyl alcohol. No one seemed to be able to answer whether it’s fine to use it with shellac, so I went ahead and mixed a small amount and the answer is YES, it’s fine to use 99% isopropyl alcohol to mix shellac. It has to be 99% IPA, though. 91% won’t work because it has too much water in it.
As far as application: I tried applying shellac with a brush and it’s a pain, mostly because I get brush marks on the wood and can’t seem to apply it evenly. It also comes on too thick. So instead I went the route of French polishing, which is really not as hard as people make it sound. I use a cheesecloth wrapped in cotton fabric (old sock, old t-shirt), I get a bunch of shellac on it and rub it on the wood in circular motion. I don’t think the motion matters as much, and I’ve seen people go in straight lines; the important thing is to make sure you never leave the applicator in one spot because it’ll stick and mess up the finish. People also seem to use some kind of oil to lubricate the applicator and that seems like a good idea – I tore a hole through my sock applicator. I use a 1lb cut and I really like it because it’s so thin. In fact, you won’t see a difference after the first application or two, but it’s worth it because it looks really nice and even at the end.
Staining shellac seems to be something that people do, but it hasn’t worked for me. It doesn’t seem to make a difference when French polishing, and even with a brush it barely changes the color of the wood. And I’ve put a lot of dye into that shellac! It was practically black! However, I saw a video of Paul Sellers applying stained shellac, and his looked pretty thick (and also heavily tinted), so if you’re after staining shellac, a thick cut would be a good place to start.
Edit: Shellac dries to the touch within minutes. Probably even one minute. However, it’s still soft for a few days, so if you place items on your shellaced piece, those items will leave marks. I let my rack dry for a long weekend, and after that I was able to put stuff on it and it was fine. I didn’t let my shelf dry for more than a day, and after that long weekend it had marks all over it.