The active agent in Darvan is polyacrylic acid. Its molecules are negatively charged along their length. They attach to clay particles and cause them to repel each other. Darvan No. 7 is a high molecular weight, long chain polymer that has been used successfully as a general purpose dispersing agent for both ceramic bodies and glazes. It is a liquid alternative to the long popular sodium silicate. About twice as much is required typically (0.4-0.5%) however Darvan does offer a number of advantages. Typically, soda ash is not needed as a complement and Darvan does not attack plaster molds. In addition slurries are much less sensitive to over deflocculation and are more stable. Source: Digital Fire.