Keum (or Kum) Boo is a process for affixing fine gold foil onto fine silver for decoration. See on my main website for more detail at this page. Up until now , I have fused the gold onto fine silver, but i’ve just tried successfully to put foil on sterling silver by depletion silvering. To pretreat the sterling sheet, I did the heat / acid/ heat / acid cycle seven times, but the end result is good. I am pleased with the result and will do more.