Continuing the discussion from Gold powder application:
I would also like to know the technique as applied to steel. Also where to buy some 22 or 24k.
The classical technique was Mercury amalgam gilding. Gold was dissolved in mercury to create a thin paste, painted into the areas to be gilded. Then the mercury was burned off turning it into a vapor leaving pure gold in the iron or steel painted areas. Not very healthy to say the least, and the artisans did not have a long life expectancy, or much brain power after a few years doing this. The fumes from this process were highly toxic.