Dear Dauvit, Keum-boo is a technique from Korea where you take a
piece of 24k about as thick as tin-foil and fine silver or
sterling that has been repeatedly heated and pickled to build up a
fine silver skin. Using a torch or hotplate, heat gently. When a
piece of clean steel alongside the silver turns blue, it at the
right temp. Lay the gold on and burnish it in place with a
burnisher. Dip theburnisher in water to cool it so the gold
doesn’t stick to it. I learned this from Dee Fontans at a
worksshop last summer. I believe Charles Lewton-Brain has a more
complete explanation somewhere in the Orchid archives.