Abstract: In the manufacture of plastic articles, particularly thermoset plastic sheets having good optical properties, by a process which involves forming the article on a surface to which the article tends to adhere, numerous and important advantages are realized by using, as a release agent which facilitates removal of the article from the surface, a salt of an addition product of a lower alkylene oxide which can be prepared by the fixation of a lower alkylene oxide on an organic material having a group reactive therewith, such as, alcohols, acids and amides, and subjecting the resulting product to esterification and neutralization.