Quote:
Originally Posted by amw896
As strange as it may seem, urine has a nitriding effect as it contains compounds which form hard crystals on the surface of metal. Sword makers in the Middle Ages discovered that steel blades quenched in urine were harder than those that weren’t."
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That peeing on the blocks is a myth though (according to the museumguides from bmw). It also has no nitriding effect. That can only occur at temps above 400C or so. But having cast iron blocks laying about for long perods of time does help, as age reduces casting stresses, so a (cast iron) block gets stronger the older it gets.