Far too delicate to touch with fingertips—just one ten-thousandth of a millimeter thick—gold leaf foil is an extremely delicate, almost transparent material. It requires a humid climate, pure water for the manufacturing process, and artisans with infinite patience. These are three things that the city of Kanazawa, Japan is known for. Since the 15th century, the region has been famous for its traditional gold leaf crafts. It still supplies more than 90% of the country’s foil.
Gold leaf is made by tirelessly beating out and stretching alloy of pure gold with minuscule traces of silver and copper. An alloy about the size of a 10 yen coin becomes the size of one tatami mat with a thickness of 1-1.2/10,000 millimeters, so thin that light seems to penetrate right through it. Touch it with your fingertip and it will cup and adhere closely to the skin, turn into a delicate powder, and vanish. Being such a fragile material, you cannot afford to lose focus for an instant in the foil beating process. Since gold is prone to becoming charged with static electricity, thin sheets of alloy are sandwiched by thin sheets of paper one sheet at a time, beat and stretched, gradually becoming thinner and thinner after undergoing a multi-stage process before being completed.
This JST Science Channel video from their The Making series annotates each step in the process with excellent details and examples:
Next: The art of Japanese marquetry, the Japanese handmade paper of Kyoto Kurotani, and from The Ring of Truth: An Inquiry Into How We Know What We Know – Atoms (1987), molten gold transforms into gold leaf.