Copper Sulphate used for browning? This Treadwell's method of browning has been prodding some semi forgotten memories, after searching through a lot of years note books I came across this under some of my notes on browning. To improve the contrast between the Iron and Steel of Damascus barrels you finely Copper plate the Iron by rubbing the clean and bright barrel metal with a cotton cloth that is dampened with a small amount of saturated Copper Sulphate solution, then dry next you swab the barrels with Ammonium Sulphate this will turn the Copper deposit a deep black then brown as normal.
This is in one of my note book's from the 1960s though I have never used this method to improve the contrast. Maybe Treadwell was going through some old browning mixtures using copper.
