From Graham Greener:
Russ,
I have the following recipes for browning barrels:
The standard recipe we use is as follows
1oz muriate tincture of steel – this is ferrous chloride
1oz spirit of wine – this is isopropyl alcohol other wise called or you can substitute ethanol, ethyl alcohol, fermentation alcohol or grain alcohol
1/8oz blue stone – copper sulphate
¼ oz strong nitric acid (concentrated)
1 quart of water
There is also a recipe for black brown or purple brown
1-1/2oz ethyl alcohol
1-1/2oz ferrous chloride
1-1/2oz mercury chloride
1oz copper sulphate
1-1/2oz ethyl nitrate with a little acetic aldehyde
3/4ox strong nitric acid (concentrated)
1 quart of water
The process of browning takes four to eight days depending on the temperature of the browning room. Either of the above mixtures are laid on to the barrels lightly with a sponge every two hours during the day and scratched off with a steel wire brush each night and morning until the barrels are dark enough. The acid is then destroyed by pouring boiling water over the barrels and continuing to rub them until they are nearly cool
