Concepts for nonaqueous deacidification with Wei T'o and precautions and techniques in application are presented as well as equipment and suppliers. The causes and effects of the deterioration of paper are mentioned as are several early aqueous methods of deacidification. The user of both Wei T'o Solution and Wei T'o Spray is requested to test design materials and papers before treatment for possible changes in appearance with the use of the product. Instructions on how to tell the pH of paper, by using Merck indicating strips, is given. See also AATA 15-329, 15-330, and 15-367. -- AATA