Amylases are the enzymes that hydrolyse and reduce the molecular weight of amylose and amylopectin molecules in starch, rendering it water-soluble enough to be washed off the fabric. Effective enzymatic desizing requires strict control of pH, temperature, water hardness, electrolyte addition and choice of surfactant.

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After desizing, the fabric should be systematically analyzed to determine the uniformity and thoroughness of the treatment. It is first weighed to determine the percent size removed. The results are compared with a sample known to have been desized well in the lab. If the size is not adequately removed then either the treatment or washing has not been thorough. Iodine spot tests are then conducted on the fabric. The fabric is not spotted randomly but from the side center-side at different points along the length of the fabric. The results of this evaluation give some idea of the causes of any inadequate treatment.