I etch first, and do it long enough till I can see a pattern. Sometimes I'll etch 2,3, or 4 times with a tap water rinse in between. Then a TSP rinse to stop the Ferric Cloride from working, another water rinse, then Laurel Mount. browning is applied. I do it only for myself and from my experience from etching the damascus knives I make. Ferric Cloride is not very strong, so I don't think you can hurt anything if it's left on a little longer. I'm not very tech minded, don't worry about temps, and when rusting just put the barrels in a small bathroom where the shower has been run with the door closed to bring up the humitidy. Don't have a tank for etching, just apply it with big cotten swabs. I suppose I should measure and record how much the F.C. is cut with water [ about 3 to 1 or what ever looks good ], temps, humidity, and all that stuff; but I don't. The barrels still come out looking ok. Just my take on doing damascus barrels, right or wrong. Paul
