acid poly ethylene imines and divalent metallic cations according to a preferred aspect of this invention the printed image is heated by passing through a laminator by laminator is meant a device which is normally used for the lamination of printed images which comprises a means of heating and pressing together the image and the laminating sheet thus causing the two to adhere commonly by passing them through a nip between a pair of heated rollers this aspect is particularly preferable because many printing and processing houses already possess and use laminators which can be applied to the materials of this invention however the advantage of this invention is that the additional expensive lamination sheet is unnecessary according to another aspect of the invention the printed image is heated by passing through a laminator in conjunction with a second inert sheet which is held against the image protective layer of the material the inert sheet does not adhere to the material but protects it from the rollers of the laminator moreover the use of a smooth inert sheet will impart a high gloss or other desired appearance to the final image alternatively a suitable choice of the inert sheet may be used to produce a pattern such as a security symbol after.