I've never really tried any air-dry glazes outside of the Sculpey brand. Back when I started making charms I scrounged around dA trying to figure out which brand of gloss to use. I remember one user tried three different glazes and all three glazes resulted in a "browning" or discoloration of their sculptures. My reasoning was: it makes sense that Sculpey products are very compatible with other Sculpey products, right? It was decided that I would stick with Sculpey brand so off to Michael's to get some glaze.
I've been using the same Sculpey glossy glaze for about 3 years now (although I've tried out their satin glaze a few times) and so far I like the results. It wasn't until a few months ago that I noticed that Sculpey unveiled a new formula. When compared to the original it appears to be more diluted and is a white-ish color instead of clear. At the time Michael's still had some of the original glaze in stock so I bought a few with a "if it ain't (yes, my Texan is showing) broke, don't fix it" mindset. Eventually I ran out of glaze and took another trip to Michael's. Obviously the stock of original glaze had been long gone so I bought one bottle and decided to try it out.
It seems watery at first, but the consistency is actually a bit of an improvement. I remember how the original formula was quite thick. Although it cured nicely in the end, I felt that the brush was picking up more gloss than it should have. You could dilute the formula but the end result wouldn't be as "glossy" as before.
If you use too many layers or you have deep crevices you'll end up with a "white-ish" finish as apposed to a clear one. Also, because it's more "watery" air bubbles are likely to form so you much be careful in choosing the type of brush you use
I have also read other reviews that the new formula causes acryllic paint to crack and some people have seen a "browning". Since I used colored Sculpey, I haven't experienced any cracking, however, like I mentioned above I am not a huge fan of the "white" finish for over-glazed areas. Overall, I haven't had a terrible experience but I will probably look for another brand.
Many people have suggested using nail polish instead... however depending on the nail polish formula and strength I've noticed it can crack. I have also heard good reviews about Triple Thick so I'm probably going to try that next.
Any other suggestions?