Your technique is good, if you see all of the lines of demarcation. Ammonium Hydroxide/Peroxide must be used within 1 hour of mixing. At least that is what we have found in our lab. So I make it up in small batches before morning evaluations and then again in the afternoon before afternoon evaluations. This is one etchant that cannot be stored, but it is the one that is used and recommended for use in microsections of printed wiring boards - plated copper deposits. Susan Mansilla Robisan Laboratory, Inc. *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************