Bill I use Radio Shack's etchant, off the top of my head I forget the concentration. I made a 4" x 36" diameter PVC pipe that has a solvent welded flat bottom cap. On the top is a slip on coupling with a threaded top to put a cap on it. I put a set of barrels in it that were 32" long and filled the pipe up with water till it covered the extension rib and then marked the outside with a magic marker. I used a solution of 15% etchant and 85% distilled water. When the solution was new I only left the barrels in there for 10 seconds at the longest. The solution is now over 7 years old and last year I did one set and it took longer to etch. I have to do another set this year, but will wait for warmer weather when I can rinse outside. After being in the solution for 10 seconds it must immediately be rinsed to stop the etching. Then card and start over again to achieve the look you want.