I did a batch of decopauge pavers last week with an epoxy layer then a screen print and put them in the blazing sun for a weekend. Needless to say there was a significant amount of yellowing. I can live with some yellowing, but in the end it is a flaw of science and materials that needs to be dealt with. There is one paver that did not yellow and that proves that it is possible to create a uv resistant decopauge for exterior use.
The image was of Caitlyn Jenner from the cover of Vogue and I have to assume that I made that coated cement piece with my UV resistant epoxy called Nuclear that I got from Douglas and Sturgess in Richmond California. This material is more fluid than the standard coating epoxy that I use and I have drifted away from using it for that purpose, but if it truly keeps these stones from yellowing I am going to go back and do some test. I have been putting a layer of glue and/or acrylic down on the washed cement squares before applying epoxy, which means this acrylic coating could also causer yellowing. The first test will be to see if the acrylic coated stones will also yellow from below the epoxy coating.
Test: Apply a coating layer of the four materials that I am using on different pavers, then coat the stones with epoxy and allow them to sit in the direct sunlight for several days. After significant UV exposure to the bright Southern California sun check the pieces for yellowing. The coating layers keep the epoxy from sinking into the stone and therefore are good to conserve the more expensive epoxy materials. The four test pieces are furniture Modge Podge, a water-based acrylic with a satin finish. A water-based adhesive glue that dries clear. A standard acrylic medium that dries clear and direct epoxy as a base coating that also finishes clear but requires more coats if used alone.
