Book 27, Question 120
How do blacksmiths change a metal's crystals?
Metal is made of tiny crystal grains.
When a blacksmith heats metal and hammers it, the grains move, squish, and change size. Heating and then cooling quickly makes steel harder, and gentle heating afterward makes it tougher. Making metal with the right grains is the secret of strong swords, tools, and springs. Forges are very hot, so this is for watching only.