INTERNET E-Mail ECD - Electronic Controls Design Inc. 4287-A SE International Way E-MAIL: [log in to unmask] Milwaukie, OR 97222 USA WEB: hhtp://www.ecd.com VOICE: 503-659-6100 FAX: 503-659-4422 SUBJECT: RE>PWB cleaning help? ------------------------------------------------------------------ Most saponifier solutions are very well buffered, and pH is a poor way to determine concentration. We have had some success with conductivity measurement for solutions in the 5-10% by volume range. Conductivity is on the high side (compared with good water) and temperature will affect readings, but most cleaning baths are at constant temperature. Of course if you drag in a lot of flux it can effect readings. Conductivity will vary with formulation (supplier to supplier) also.