Substrate impregnated with a substance and with an indicator that visibly reveals when the drug is inactive

摘要

The invention is a method of indicating the presence of an impregnant, e.g. an antimicrobial composition, in cloth to provide visual evidence of the continuing activity of the impregnant. The antimicrobial composition in the cloth is activated on contact with a liquid such as water and is ionically bonded to the cloth. Small portions of the impregnated cloth are dyed with an indicator dye which bonds preferentially to the antimicrobial composition so that when the antimicrobial composition is exhausted, the dye will disappear from the cloth. The dye is preferably applied to the cloth in stripes.