The Measurement of the Amount of Isopropyl Alcohol in Fountain Solution

Determination by Refractive Index

Abstract

In lithographic printing, it is well known to apply a specific gravity (S. G.) for the measurement of the amount of isopropyl alcohol (IPA) in the fountain solution. The fountain solution usually contains a small amount of desensitizer with IPA. As a S. G. greatly depends on temperature it is difficult to determine the accurate amount of IPA. Some unavoidable errors occur during the S. G. measurement, caused by ink scum, dust and bubble. We studied many methods for the accurate measurement of IPA concentration in the fountain solution: S. G., pH value, electric conductivity and refractive index (Brix%). As a result, we found that Brix% is the best way to measure an accurate amount of IPA, independent of a small amount of desensitizer.