even when the aim of a microencapsulation application is the isolation of the core from its surrounding, the wall must be ruptured at the time of use. many walls are ruptured easily by pressure or shear stress, as in the case of breaking dye particles during writing to form a copy. capsule contents may be released by melting the wall, or dissolving it under particular conditions, as in the case of an enteric drug coating. in other systems, the wall is broken by solvent action, enzyme attack, chemical reaction, hydrolysis, or slow disintegration.