TIN (stannous chloride) blooms or brightens colors, especially reds, oranges and yellows. Almost always used with cream of tartar 1/2 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.