Democratic Sentinel, Volume 16, Number 5, Rensselaer, Jasper County, 19 February 1892 — To Harden Iron. [ARTICLE]

To Harden Iron.

Ox- hoofs and leather are soaked in French nut oil, and are then burnt, pulverized, and mixed with sea salt and potash. The following proportions are used: 30 per cent, of hoofs, 30 per cent, of leather, 30 per cent, of sea salt, 10 per cent, of potash. This product is said by the Scientific American to harden iron all through.