Hi Sarah, I'd have to agree with Mark 110%. We had two manual valves until the ammonia gas ran out one weekend and the etch solution back filled the gas line. Nothing like blue crystals in the gas line. We use a Walchem W-150 pH Controller. They have a newer model: W-320, quoted me around $1000 but, I have to go through a local rep. Here's their contact info: Walchem Corporation Five Boynton Road Hopping Brook Park Holliston, MA 01746 (508) 429 - 1110 Tel. (508) 429 - 7433 Fax Hans Air Force Material Command - We keep them flying! ~~~~~~~~ Hans M. Hinners WR-ALC/LYPME Bldg. 640 Materials Engineer 380 Second Street, Suite 104 Manufacturing Eng. Sec. Robins AFB GA 31098-1638 912-926-1970 (Voice) 468 - 1970 (DSN) 912-926-7974 (Fax) [log in to unmask] > Hello everybody > I would like to add a pH control system to my ammoniacal copper etcher > that would open and close a vent based on the pH of the bath. Does anyone > know of a company that supply me with something like that? > Thanks > > > Sarah Boutwell > Manufacturing Engineer > Johnson Matthey Advanced Circuits > [log in to unmask] > 612-684-5079 > ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################