Good information Ken. I had an employee who was doing the process in my shop for about 5 years. He got excellent results but it was very labor intensive. He usually had 15 or more passes and he also reduced the acid strength as the number of passes increased. I believe he stuck with stronger acid for more passes than you are using. This may very well have contributed to amount of work required with his process. I'm getting ready to give it a go myself and I'll give your method a try and report back.

Are you using a 3% ferric chloride dip for all stages or just the first dip? My former employee varied the strength of the Ferric Chloride as well as the strength of the acid.

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