Let's talk a little about polymer clay varnish
After much internet research and testing, I've found Varathane to be the best varnish to date. Look for, "Varathane
Crystal Clear Water-Based Polyurethane Heavy Use Formula". It comes in a
choice of Gloss, Semi-Gloss and a Satin formula. Mine was purchased from my local Ace Hardware in the half pint container.
Varathane comes in water based and oil based versions. When using this varnish for polymer clay make sure you purchase the WATER based version.
Let me start by saying I don't use varnish on the majority of my projects. Baked polymer clay is durable. It holds up to washing, wear and weathering.