Critical Dilution is the phrase that we use on the wiki to refer to the dilution below which adding more detergent has rapidly decreasing influence on the soap film thickness. Currently, critical dilution is a fairly rough but useful measure. For Dawn Pro and its equivalents, the critical dilution seems to be somewhere around 16:1. It is influenced by pH for many detergents as the effectiveness of many surfactants is heavily influenced by pH. This article is a . You can help My English Wiki by expanding it.