water glycerol poly ethylene glycol and silicone oil with mixtures of water and glycerol being especially preferred in addition to pre polymer the pre polymer solution will contain a cross linking agent unless the pre polymer is bi or multi functional so that it can cross link without a separate agent those skilled in the art of polymer chemistry recognize that many crosslinking agents exist and that their selection depends upon the functional groups or reactive intermediates on the polymer with which they are intended to react examples of cross linking agents are provided below in descriptions of preferred processes for forming the network polymer the pre polymer solution also may contain viscosity modifiers a viscosity modifier may be used to control the amount of solution that remains on the substrate after draining or blotting which in turn affects the thickness of the coating an especially preferred solvent system is about two parts water and one part glycerol whose viscosity is such that it may be used advantageously without a separate viscosity modifier the selection and use of viscosity modifiers is well known in the art in addition to the above described components of the solution the solution may further contain any additives that do not inhibit the curing such as.