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 SUBJECT:   RE>PWB cleaning help?
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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.