If I ever write a book on finishing, I’ll probably call it “Farting Around With Finishes.”
One of the things I like to do on a Sunday afternoon is mess around with dumb ideas. About 100 percent of the time, my results are ugly or unremarkable. But every once in a while I discover something interesting that eludes the rounding error of “about 100 percent.”
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One of the things I love about old vernacular pieces are the (rare) unrestored finishes. The best of them have a dark and mellow glow that verges on black. They have a low luster, but it’s nothing like dried linseed oil, which can look flat and starved.
After talking to experts on furniture and finishing, I’ve concluded that many of these finishes are the result of soot from the hearth (consider what coal soot did to the buildings of the U.K.). And the shine? Burnishing from use and the natural oils from the body of the sitter. There also could be waxes. Grease from food. Soil from clothing. Water damage. Children. And on and on.
(The original finish on these pieces could have been anything from nothing/nekkid, to an oil, a linseed-oil paint or a wax. These made-at-home pieces were unlikely to have a fancy film finish applied by the builder, though anything could have happened to the piece in the 20th century.)
Last fall I took a trip to Europe to travel around with Chair Chatters Klaus Skrudland and Rudy Everts. We drank a lot of Belgian ale and talked non-stop about chairs for about a week. Near the end of the trip as we were driving back to Munich, I wondered aloud if it would be possible to create a finish that would somewhat mimic old finishes on vernacular pieces (without dangerous chemicals or a 32-step process).
I had a dumb idea. Perhaps the finish could be based on a plant oil that is similar to sebum, the oil and waxes made by our sebaceous glands to keep our skin moisturized. As it turns out, jojoba oil is similar to sebum. (There is synthetic sebum out there, but the sources I have found are too expensive to use as a furniture finish.)
Jojoba is inexpensive, widely available and edible (but not digestible). Like linseed oil, jojoba is a drying oil. It is combustible, and there is a small risk of it auto-igniting if you foolishly bunch up your rags. So take the same precautions as with all drying oils and dispose of the rags as recommended on the oil’s Safety Data Sheet.
So jojoba is indeed a good candidate for a wood finish.
The next hurdle was how to get the hearth smoke into the finish. My first thought was to grind up lump charcoal or simply get some ashes from the fireplace and mix it into the jojoba. My experiments with those sources didn’t go well. The finish felt really gritty.
The solution was to switch to carbon black. Carbon black is essentially soot that is used as a pigment in inks and paints, and to color the rubber in your tires. It’s cheap, and you can get it as an extremely fine and consistent powder.
So what happens when you mix together jojoba oil and carbon black? I started with 1 ounce of jojoba oil and mixed in 1/2 teaspoon of carbon black. I stirred it with a popsicle stick and within a few seconds the carbon black was evenly distributed in the oil.
Then I ragged it on a scrap white oak chair arm that has been hanging around my shop for a year.
Surprisingly, it looked pretty good. The oil gave the wood an orange color, and the carbon acted like a pigment stain – collecting in the wood’s pores and sitting on top of the wood. I let the finish dry for a couple hours then checked it again.
The downside is that the carbon black rubs off on your clothes a bit. After the oil dried to the touch, I rubbed it quite a bit with clean, dry rags. The finish on the wood didn’t get any lighter, but I continued to get some carbon black on the rags. (Though it was less and less the more I rubbed.)
So next, I’m going to reduce the amount of carbon black in the mixture and see what happens. And I’ll try adding a spit coat of shellac to the sample boards to see if it locks in the black color. Third option: cook up some soft wax with jojoba, beeswax and some carbon black.
All this might be a dead end, but I enjoy the process (and I hope that maybe Lucy will get me a lab coat for Christmas – ooooh, and a clipboard).
— Christopher Schwarz