Tin – Stannous Chloride

This is tin (stannous chloride) for use as a mordant on fibers for natural dyeing.
I read that scarlet could be achieved by using tin as a mordant with cochineal, with a bit of cream of tartar.

Tin blooms or brightens colors, especially reds, oranges and yellows. Almost always used with cream of tartar — ½ ounce tin and 1-2 ounces of cream of tartar for a pound of wool. Simmer for an hour and rinse in soapy water before dyeing. Tin is a good additive mordant. Store wool wet or dry. Too much tin makes wool brittle. It is caustic, be sure to handle carefully and clean up thoroughly.