Control of pH levels in the stock preparation section of a paper mill is essential to the process of effective papermaking.

 Although pH is also controlled upstream of the headbox, the last opportunity to control the pH of the pulp slurry occurs at this location.

The headbox is the first wet end component of the paper machine, and headbox stock has high suspended solids.

 pH measurement in this location is difficult because sensors are prone to clogging and fouling, equiring frequent cleaning and replacement. Despite these problems, the benefit that pH control conveys in strength and other paper properties are so great that headbox pH measurement cannot be ignored.

Recent improvements in probe design have taken the hassle out of making this measurement.