The gold foil may be made by rolling a piece of 24k gold as thin as one can go on the mill and then continue to roll it with in between annealings. An alcohol lamp or even a cigarette lighter may be used to anneal the gold when it is this thin. Some people continue to roll with a piece of paper or metal on each side of the gold to increase the pressure on it. I usually use a piece of sheet metal at the end to increase the rolling pressure. When the micrometer barely measures it it is quite thin (.001 mm). Most failures in adhesion with keum-boo in my opinion come from too thick a gold foil being used.