How do I apply the metal browning / iron staining finish?
Jim uses a tannic acid process. The full write-up is at jimkibler.net/blog/archives/10-2014. Iron nitrate crystals are used in this process. The Jax Black product labeled 'for brass' is what is used on iron, the label is misleading, it works the same on iron/steel. Jax Brown is for actual brass hardware.