This September, I attended the Port Townsend Wooden Boat Festival. I’ve been going every year for a few years now and thoroughly enjoy the woodworking classes that they put on throughout the weekend. One of the presentations that I went to this year was called “Non-Toxic Finishes” and was presented by Steve Habersetzer of the Port Townsend School of Woodworking. Of all the presentations that I attended this year, this seems to be the one that has stuck in my mind.
Steve explained that any finishes with thinners in them caused him to have an allergic reaction. If my recollections are correct, he advocated linseed oil. The funny thing is that it was not the issue of toxic versus non-toxic that resonated with me, rather it was the method of application. Perhaps this is common knowledge, but it was the first time that I had heard about heating a finish to apply it. I just had to try it!
For some time now, my go to finish has been Watco Danish Oil. I wanted to do a little experimentation with heating it prior to application. First let me be clear, this is not what Steve was talking about in his presentation, as he was talking about linseed oil. I don’t want to give the impression that this is a non-toxic finish, or that what I am doing here is in any way what he advocated.
On my workbench build, I have just finished making all of the chops for my vises. They need to have the finish applied before I screw the vise face plates to them, and before I glue the leather to the inside faces. I thought that this might provide an excellent opportunity to experiment with a heated finish.
I didn’t think that heating the oil directly would be safe. I also didn’t think that the Mrs. would appreciate me using her crock pot, so I set of for Walmart in search of a cheap one for the shop. I was quite surprised, I found a small 2 quart crock pot for under $10, wow.
I filled it with water about 1/3 up from the bottom and then placed a jar lid in the bottom of the pot. In a separate clean jar, I added the danish oil and a little bit of mineral spirits. I suppose that it was about 3 parts danish oil to 1 part thinner. Perhaps I shouldn’t have added the thinner as I am adding another variable that I normally don’t use, but that’s what I did. I capped the jar with a lid to prevent steam or condensation getting into the jar, but left the lid lose to allow for expansion or off-gassing.
I placed the jar into the crock pot and sat it on the jar lid in the bottom of pot. This might not have been necessary, but I did it to avoid direct contact between the jar and the pot. I put the glass lid on the crock pot and left it for about a half hour.
While it was heating, I spread out some newspaper on my assembly table (OK, so it’s really a table saw) and found some scrap off-cuts to set the chops on.
I started to brush on the oil and was a little surprised at just how fast it was soaked up by the wood. When I apply danish oil, I always keep adding more as it soaks in. I keep this up until the wood will absorb no more. The fist application is always far heavier with danish oil, but this one really took a lot.
It took me about an hour to do all four vise chops. I kept cycling through them adding oil wherever it was needed. That jar that I showed above? I used it all. I couldn’t believe that these four chops would soak up that much finish. I left the surface wet for about 30 minutes and then thoroughly dried everything with a rag. My experience has been that you don’t want to leave any wet oil on the surface or it will turn gummy.
With every thing wiped down, I left it to dry/cure.
I have since added a second coat, but this was applied or rubbed in with 220 grit paper. That has been drying for two days now and I’ll probably do a third coat with 320 grit paper tomorrow. A fourth coat, rubbed in with 400 grit is usually as far as I go, other than some furniture paste wax when everything has cured.
I don’t think that there is sufficient information to make any conclusions yet about whether or not heating the oil yields a superior finish, but I intend to keep experimenting along these lines. I was pleasantly surprised to see how much better/faster the oil soaked in. I think I got significant end grain penetration of the oil. I did sort of mess this test up a little by adding the thinner, and I suppose that I could try it again with straight danish oil that has been heated.
It will be interesting to see if heating the oil helps to speed the cure time, which is reportedly the other major benefit to this method of application in addition to the superior penetration. I’ll report more later.
For $10, the crock pot seems full of interesting potential. I might take a crack at mixing my own finishes; could be fun and interesting. I also ordered some bees wax to test another idea I had. I’ll try to post about that tomorrow.
– Jonathan White