Having tested, erred, retested, erred again and so on, I was finally happy with how the homemade japanning came out, so did several restores.
We’ll try and do a summary of everything learned here in one blog post.
Asphaltum—available in powder form or liquid, which is what I used. Art supply stores seem to be the best source, as it is used in acid etching.
Solvent—Xylol or turpentine should either work fine. Both are capable of suspending the heavy asphaltum solids.
Varnish—I used semi-gloss spar varnish that was already on hand. Other recipes I found used gloss or BLO. I might have to try BLO sometime in the future.
Artist brush—A small mop brush (about 1/2in wide) worked very well. Make sure to get one that is recommended for oil paints and finishes.
Air-tight container for mixing and storing the japanning mixture
Shop supplies—such as sandpaper, paper towels, masking tape
When all was said and done, there was about $30 invested in supplies, outside of normal shop stuff.
2 parts liquid asphaltum
1 part spar varnish
Mix well. The ratio doesn’t have to be exact as I also had success with a 3:1 ratio, but make sure it is thick enough that it will coat and cling to vertical surfaces. If the mixture is too thin, it will sag and is susceptible to bubbling when baked.
The liquid asphaltum is a 50/50 mix of xylol and gilsonite,by weight, so if you purchase the powdered asphaltum, you should end up using nearly equal amounts of the three ingredients.
One issue that came up is that the liquid asphaltum will thicken after being opened, even in the original container. Adding a splash of solvent will easily get it back to a usable consistency.
Starting with a stripped and cleaned metal surface, lay down an even medium coat of the japanning mixture using the artist’s brush.
Allow the finish to dry overnight.
Bake at 250-300F for two to three hours. Indirect heat is best, such as an oven. When using the grill, I did get some bubbling where part of the plane was directly above a burner. The areas around the lettering were much more susceptible to this. To avoid that issue, I used the side burner(s) and place the plane body in the center of the grate so that it wasn’t directly over the heat source. Also, baking for longer &/or at higher temps may result in an even harder and shinier finish. If you want to do higher temps, go progressive, i.e. two hours at 250, two at 350, one at 450. Starting at too high of temps may cause bubbling.
After allowing the plane to cool, scuff the finish with sandpaper. 220 grit seemed to work best.
Wipe the finish down with a solvent dipped rag or paper towel to remove sanding dust.
Repeat the process to add more coats.
Three coats seems to be about right. It allows the finish to fill the unevenness of the casting while preserving the details of the lettering. I tried a fourth coat once, but it caused the lettering to lose its clarity.
A note about masking. On early attempts, I was masking all the surfaces not being japanned. The problem is that the tape has to be removed before baking and then reapplied. Later in the process, I didn’t mask at all and didn’t have any issues. Any japanning that ended up on the sole or sides was removed with a razor blade scraper before flattening, which removed any left over traces. The frog mating surfaces were carefully “painted” around and the very little japanning that got on those was again scraped off with the razor blade.
Having used both spray paint and now playing around with this method of japanning, here are my conclusions.
What I like about japanning:
The end result seems to match up a bit better to the original Stanley finish.
The whole process can be done inside.
It fills the iron castings very well.
The japanning mixture goes a LONG way. I have now done the equivalent of six planes (four complete, with two done twice) and have probably used about 20% of the liquid asphaltum. Considering the size of the planes done (#5 & 6 each once, 5 & 8 twice) a single pint of the asphaltum should easily do two to three dozen plane bodies.
Considerations before japanning (not necessarily negatives, but things you would want to think about):
The japanning finish is best done in a dust free environment.
The whole process will take several days to complete. The individual steps do not take that long (I was able to scuff, wipe and apply a coat of japanning on three planes in less than 20 minutes total), but you have the time to allow the finish to dry, then bake, then cool before doing the next layer.
Must have the ability to bake the finish without being kicked out of the house.
Requires the purchase of some materials that probably won’t be useful for much else.
I think there are times/circumstances when both spray paint and japanning are appropriate. If you are the type that just want to get the tool protected from rust and move on to using it or you are just doing a couple of items, then spray paint is probably more for you. For me, I actually enjoyed the whole process, so am inclined to continue with japanning. I’ll probably play around with some aspects of japanning (such as using BLO instead of varnish) just for the fun of it. If anything interesting comes up, I can add another post, but otherwise, this blog series is a wrap.
Thanks to those of you who followed and encouraged during this blog. Special thanks to Don and Mads for providing links with lots of great information. If anyone does attempt this process, please let me know how it goes and if you learn something I missed.
-- "The American Republic will endure until the day Congress discovers that it can bribe the public with the public's money." Alexis de Tocqueville, 1835