This document specifies a test method for the determination of the solubility of a water-soluble pressure-sensitive adhesive in water or the solubility of an alkali-soluble pressure-sensitive adhesive in alkali by measuring the loss in mass of the adhesive when immersed in water or alkali. The solubility of the adhesive is one of the key factors in assessing the possibility of recycling products to which labels are fixed using a pressure-sensitive adhesive.