Japanning when restoring tools...

I went down the youtube rabbit hole the other day, after watching the videos linked in the "repairing hand tools" thread. I came across the technique of "japanning".

It is not, apparently, anything to do with japan. It was a European technique to imitate the black lacquered items coming from japan, and is unrelated to the Japanese methods.

Various recipes were used, but the are basically

Powdered bitumen/asphaltum
Linseed oil
Turpentine

It is mixed thoroughly and allowed to stand for 24 hours or so to thicken to a paint like consistency. Painted on to metal work, which is then baked.

Baking is a series of incrementally hotter stages, allowing to fully cool between steps, starting from about 200f for an hour, then stepping up to 250f, 300f, 350f, 400f - each held for an hour and allowed to cool between stages. In the curing process the turpentine and the bitumen power forms chemical bonds, essentially polymerising like a tough plastic. The oil adds flexibility so that the finished product doesn't end up cracking.





I love the look of the finish it produces.

Excellent topic and videos. I'd never heard of this process before but, I am taking a much closer look at my old tools. Thanks for sharing!

Nice finds! I've been curious about various methods of tool blacking.

Most toolmakers do some sort of chemical black treatment before sale.

I try not to remove the black part of tools when I restore them. I just gently clean off the surface rust with a wire brush, or even just a rag and oil. Some people like to get that shiny steel look, but in my locality that will rust in a New York minute, even with a coat of oil over it. It might not look brand new, but it stays strong longer.

If I knew how to properly black tools, or use this Japanning process I might be able to get the brand new look!

One of the sets of videos I was watching had a guy that routinely blackened all the small metal parts - screws, bolts, nuts etc...

His technique was wonderfully simple. He just heated them up with a blow torch and dropped them in a mineral oil. They come out with a lovely consistent blackened surface, which provides a degree of corrosion resistance. I'll see if I can find the process.

Found an explanation/demo



He uses used oil, but it seems to work just as well with new oil. They oil burns in contact with the metal to form the polymerised carbon layer. I guess you could carefully do repeated layers to build up a tough finish.