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With the visual/feel method, when the reaction slows down, how do I know if I need to add more HCl or H2O2?
Bertho
From: James Sent: Monday, May 12, 2014 21:18
FWIW, I use 35% H202 to reoxygenate my CuCl2, 1 cap in about 500ml of the etchant before I start, and now and then add a cap of HCl.
Unfortunately my CuCl2 had a pretty rough adhoc start to life and no measurements were taken, but it works. It's on my list if jobs to one day start a new batch with a bit more care and record it for posterity.
When I do so, being of a "do it by feel" kind of person, I intend to start with a small amount of HCl (33%) and add (contrary to good practice, but necessary when done by observation) sufficient water until fuming is no longer evident, then add and mix 35% H202 1 cap at a time, until a wad of copper wire strands is being dissolved at a moderate rate, leave this to consume the copper and develop the characteristic green coloration (adding more copper or H202 as required). Therein simply maintaining this useful rate of etch in normal operation by addition of small amounts of H202 and occasional HCl to renew the CuCl2 which has developed, as is my current practice. I'm fairly confident that this simple observationally-based process would give a good result without the need for introducing maths, careful measuring, and chemistry equations into it :-)