ericw93•23d agoProlific Poster

I always thought the old 'quench in urine' thing was just a gross story, but a guy at the Montana forge meet last weekend showed me a real 18th century document that listed it as a hardening step for certain tools.

3 comments

3 Comments

What kind of tools did the document say it was for? I've heard it was sometimes used for files or springs. Did the guy have any idea why urine over water or oil?

grantw4123d ago

Urine's acid helps cut steel, water just rusts it.

margaret73623d ago

Hold on, "urine's acid helps cut steel" is a huge overstatement. The ammonia in old urine might help break down rust or act as a light cutting fluid, but it's not actively cutting the metal. Water with a proper soap or oil works way better for lubrication and cooling without the mess and smell.