I use the polyurethane called Varathane (water wash-up, glossy, with IPN, UV resistant --there are 4 versions, 2 of which are water-based, but that's the one with IPN). It's probably the gloss finish most commonly-used by more experienced clayers, along with some who like Future/Pledge --aside from sanding and buffing to get a gloss finish (many high-end clayers do both
the Varathane and sanding-buffing for the most sublime finish).
Fimo's "mineral/spirit-based" gloss finish is/was probably the best one out there but it's very very expensive for even a small amount. It also looks like it's finally been discontinued though you might still be able to find some online. (Fimo's water-based finishes aren't-weren't very good though, surprisingly.)
Sculpey's Glaze*** (see changes to this product below)
finish is rather thick and gloppy and more susceptible to bubbling during curing, though many crafter-clayers aren't aware of the other finish possibilties so many use it.
Also, Polyform has recently put out a new brand of clay called Studio by Sculpey
, and with it, a "new" version of both gloss glaze and liquid clay under the Studio
(Premo doesn't make a finish that I'm aware of. Premo is manufactured by the Polyform people who also manufacture the Sculpeys, so they probably don't want competition for their Sculpey Glaze and "new" Studio finish. Premo is quite a different clay than Sculpey though --originally created to the specifications of a clayer, not Polyform's).
All of those liquid finishes are water-based except the one that's alcohol-based, so no fumes/smells/dangers for any of them.
(You wouldn't want to use a petroleum
solvent-based finish --anything that cleans up with mineral spirits, etc-- directly on polymer clay anyway because it would eat into the clay over time.)
As for walking into a store anytime, the only one you'll find quite that easily without doing a little checking is Sculpey's Glaze unfortunately.
Once you buy a quart
of Varathane, or a bottle of Future, though they'll both last a reee-e-ally
long time. Even if you can find only a gallon size of Varathane, clayers generally decant Varathane into a smaller container to use (with an air-tight lid). That keeps the stock in the original can from getting thicker from evaporation over time, and the smaller container is just easier to deal with. (I use baby food jars and old spice bottles, etc.)Varathane
can be found in various hardware stores, particularly ones like Tru-Value and Ace, but some people have reported finding it at Walmart and a Sears Hardware
store at some point.** (There's a store locator on the Rustoleum website that might help too.)
Check out this page for more info about finding Varathane, as well as ways to apply it, etc. (and info about the other finishes as well
(...click on Varathane
**sometimes store clerks will say they don't carry Varathane, but it's usually just in a different place than they expect --generally with the other polyurethanes, for sealing bare wood
polymerclayexpress.com even has it in a 4 oz version (a lot more expensive by volume than buying at a hardware store though)http://polymerclayexpress.com/finish.html
And I've been told that the Kelly Moore paint stores carry a brand of polyurethane that also has IPN... it's called Kelthane
.***edited later to add
: The original Sculpey Glaze
has now been changed to a polyurethane (now looks milky in the bottle instead of clear). It may even be one with IPN, but don't know for sure. It may come in both Gloss and Satin.....The Studio by Sculpey
line also has a polyurethane in a small bottle. (Both are still a lot more expensive than buying at a hardware store tho.) Future
-Pledge can sometimes be found at grocery stores, but more often at places like Target, etc. (The U.S. version has recently been acquired by the S.C. Johnson people, so the newer bottles are being called Future/Pledge or something like that, but are the same formulation.)
There are other polyurethanes and other acrylic finishes that can be used to give gloss too as well as other materials like 2-part epoxy resins or glues, plus white glues and "dimensional" white glues, acrylic mediums*, clear embossing powders, etc., but those often aren't as unscratchable as Varathane and Future, or they're much fiddlier to use.
I should have added that I do use Future
I use it when I give classes because it is thin, and so it dries quicker than Varathane which can be important when time is tight. I can also apply it very quickly by just putting some on a cloth or even in my hands, then rubbing the items all over. And it's probably even
cheaper than Varathane.
I've also used it on still-warm clay
to just give a little sheen to an item rather than a heavy gloss... it really sinks in fast so doesn't pool on the surface that way.