Oscar Gaddy's last article in DJG before his untimely death dealt with the original Parker black and white process and how he, Oscar had tested and modified it. Included in the article are several good pictures and comments on the use of an "etch", whether it be ferric chloride, dilute sulphuric acid, or other. As one who is trying to teach himself this process, I have observed a difference from barrel set to barrel set, even one barrel over another in the set, most likely due to the composition/%iron vs. steel. Finally, polishing/sanding obscures the pattern. The "etch" or "browning" solution causes it to reappear as a pattern as the iron is "blackened" at a differentialy rate to the steel in the barrel. Best, Dr. BILL