Cernit Varnish is produced in Belgium by The Clay and Paint Factory. Clay sealers can have very different effects when used on different types of polymer clay. You should test before using on production work to ensure it will deliver the effect you want.
A thorough evaluation of many different clay sealers was conducted by Ginger at The Blue Bottle Tree - Testing 41 Polymer Clay Sealers.
Cernit Varnish is water-based and does not have any extra shipping requirements.