Finishes
Pure polymer clay doesn't require any sealant or finish. In fact, many polymer clay artists prefer the look and texture of unsealed clay. However, certain surface treatments (such as metal leaf and some inks) are not as durable as polymer clay and may require a protective finish. Other projects simply look best with a high gloss. The quickest and easiest way to achieve a glossy finish on polymer clay is to apply a sealant.
Some finishes don't work well with polymer clay. In fact, some will never dry or "eat" through the clay, leaving a gooey mess. Even worse, the finish may seem to be fine for months before disaster strikes. There are frightening stories on-line about months' worth of work disintegrating as a result of incompatible finishes. Fortunately, artists and hobbyists have experimented and found several sealants that have been giving satisfactory results for over ten years. Below are some of the alternatives:
Varathane
Future Floor Polish
Fimo Lacquer
Sculpey Glaze
Poly Glaze
Other Finishes
Links
Glass Attic: Finishes and SealersCompiled by Diane Black
http://www.glassattic.com/polymer/finishes.htm
Polymer Clay Cyclopedia: Finishes
Check out the links to finishing tips from PCC members and Sarajane Helm's information about Varathane.
http://www.polymerclaycentral.com/cyclopedia/finishes.html