parts by weight per 100 parts of the unsaturated material of a crosslinking agent of a multifunctional unsaturated free radically polymerizable material examples are triethyleneglycol bis methacrylate ethyleneglycol bis methacrylate bisacrylamide and triethyleneglycol bis acrylate with the former being preferred in amounts from about 0 75 to about 1 5 parts the initiation of the polymerization within the precursor is facilitated by the presence of at least 0 1 part by weight per 100 parts of the unsaturated material of a free radical initiator which is soluble in the polyhydric alcohol the initiator may be of the thermal or photo class the actual selection is dependent on the monomers and the polyhydric alcohol examples of useful thermal initiators are benzoyl peroxide azobisisobutyronitrile di t butyl peroxide and cumyl peroxide examples of useful photoinitiators are disclosed in the article photoinitiators an overview by g berner et al in the journal of radiation curing april 1979 pp 2 through 9 the preferred photoinitiator is benzildimethylketal it will be recognized by one skilled in the art that other additives e g tackifiers such as polyacrylic acid may be added to the precursor without departing from the spirit of the invention the essentially solventless precursor can be.