I finally discovered a decent method for spraying on japanning. For more information on japanning, check out my original video here: https://youtu.be/SBqgpdBNrt8
Spray Japanning Recipe:
60% Turpentine
25% Asphaltum/Gilsonite
15% Boiled Linseed Oil
Mix together (not in the spray bottle) and set aside for at least 24 hours. Check if consistency is spraying to your liking, and add more turpentine if too thick or more asphaltum if too thin. Wait at least 24 hours after the addition of any further ingredients before use. The recipe is only in percentages and not by weight or volume because different quality turpentine and asphaltum will produce slightly different results, so use the percentages as a general guideline.
Once ready to paint, do not stir or shake the japanning as undissolved particles will be at the bottom of the container. Pour ~75% of the container of japanning into either a spray bottle designed for thick liquids or a re-fillable spray can that you pressurize with an air compressor. I am sure using a HVLP spray system would work here as well, but I wanted to make this as accessible as possible.
Spray on one thin coat and let sit for a few hours before baking so that any runs or dips have stopped. Place painted item in cold oven and set it to 200F for 1hr then let cool. Bake it again at 300F for 1 hr and let cool in the oven. Then bake at 350F and finally 400F for 45 min each, cooling in between steps. If japanning is still not hard after 400F, you can bake at 425F for 1 hr. If you are using a toaster oven, you may have to bake for longer as the toaster oven is not as well insulated as a home oven.
Once fully hard, you can smooth out the first coat with sandpaper and apply further coats. You can also apply further coats before you bake past 300F, if you think your first coat is smooth enough. Spray japanning will require more coats than if brushed on. If the end result comes out with a lot of large ripples and not smooth, then you either put a coat on too thick or you baked the japanning at too high a temperature, too quickly. Either sand down and apply a thinner coat with the same baking instructions or increase baking temperature intervals to 50F segments.
Keep the unused japanning in a container with a tight lid. If the japanning starts to get too thick or hardens, you can always add more turpentine to bring it back to life.
I hope to put this out there so more people try the recipe and experiment with it so that we can all get as close as possible to a working recipe.
You can follow along on the traveling hand plane here:
https://www.youtube.com/c/WoodWright/
https://www.youtube.com/channel/UCHsqqRjziUaMwZgQZHw-n1w
https://www.youtube.com/c/RexKrueger
https://www.youtube.com/c/GreenBeetle
You can find more details on Japanning here:
http://www.cranialstorage.com/Wood/japanning.html#Japan-Metal
http://www.inthewoodshop.com/ToolRestorations/ColdCureJapanning.html
https://www.lumberjocks.com/JayT/blog/32704
https://books.google.ca/books?id=gZgXTVwhRvIC&pg=PA2&dq=japanning&hl=en&sa=X&ved=0ahUKEwiV2tTC8N_jAhWGct8KHUCNBnMQuwUIKjAA
https://www.2ndusss.com/uniforms-and-gear/an-actual-japanning-how-to-yes
https://books.google.ca/books?id=xV0OAAAAYAAJ&printsec=frontcover&redir_esc=y#v=onepage&q=japan&f=false