The next step in trying to come up with an acceptable japanning recipe/method was to test some blends of finishes. Internet research turned up a few possible recipes, mostly involving powdered asphaltum/gilsonite dissolved in a combination of turpentine and BLO &/or spar varnish. The woodcentral link Mafe posted in the first installment has one and fellow LJ Derek Cohen has mentioned a similar recipe he uses. Well, the reason I went with the liquid asphaltum was that it takes care of the intial step of dissolving the powder by having it in the xylol solution. You could just as easily purchase powdered gilsonite and dissolve it yourself over the course of a couple of days.
In testing, I tried adding various amounts of spar varnish to the asphaltum, painting on a plane bed and letting it dry overnight. Here is one such test comparing a 2:1 asphaltum to varnish blend with the pure liquid asphaltum.
This ended up being the ratio for my first attempts. The addtion of the varnish helps thin the mixture a bit so that it is easier to apply and flows much better and I also found it seems to slightly lengthen the intial work time so that the solvent doesn’t flash out before allowing the japanning to self level. If you thin the mixture too much, it doesn’t coat the vertical surfaces well and will sag before setting up. (Hint: that would be one of the abject failures mentioned earlier)
Before continuing further, I need to ask for some leniency and understanding. I didn’t set out to write a blog when first attempting to figure out this process, so didn’t do a good job of documenting & photographing everything along the way. For the pictures I have, you will see several different planes used. These are all planes that have gone through my japanning process and I have tried to pick photos that best show what was going on at various stages.
Carrying on. After working with several different asphaltum to varnish ratios, ranging from 1:1 to 4:1, I settled on 2:1 as the best combination of coverage, flow and appearance. I used semi-gloss varnish to try to tone down the high sheen of the asphaltum. My test bed was a Bedrock 605 that needed a complete makeover, so it was masked off and a light coat of japanning applied. Here it is part way through laying on the first coat.
You will notice that the brush is not the same as those pictured in the first blog installment. I first used a flat brush to try and get into the nooks, crannies and corners of the plane, this thinking was to change later. In spite of the asphaltum looking black in the can and jar, it is really a dark brown. If you look again at the picture of the test, you may be able to see that the thinned finish has a slight brown tinge, while the undiluted asphaltum is nearly black. The light coat that was applied really shows the actual brown color.
The plane was set aside to dry overnight before a second coat.
Before you jump right in and follow these steps, please note that this plane got completely stripped and redone again a bit later. It turned out much better the second time, using things learned from this first try.
We’ll leave it there for now and pick up the next installment with more coats, application errors and attempts at curing the finish.
-- "Good judgement is the result of experience. A lot of experience is the result of poor judgement."