Moonies are imperfections on the surface of cured polymer clay. Many causes…but I have read that it is mostly trapped air and/or moisture. Moonies look like little whitish blisters on baked clay. Moonies seem to be a common problem for all polymer clay doll makers.
I think it is best to try to avoid moonies. Here are the many suggestions I have heard about on how to eliminate trapped air; be sure to press the clay tightly onto the wire armature ; when adding clay to the sculpt, press and roll the edges firmly; examine the clay surface carefully before baking and If you see a little pale spot on the sculpt, prick with a pin and press to expel trapped air; when using crumpled foil as an under-sculpt, be sure to compact the foil to expel all trapped air; and when using a press mold, push the clay halves together and seam firmly so that no air gets trapped inside. Some say that the longer the uncured sculpt sits around, the more you end up with dirt, moonies and other imperfections that show up on the surface of the cured clay.
So what to do if you have moonies? You may want to try to save your sculp…First use a knife and carefully scrape out the imperfection. Then, wet the area of the repair with Liquid Sculpey. Fill the void with the same blend of polymer clay you used on your sculpt. Be sure to feather the clay into the surrounding cured clay. Then use your heat gun to set the fresh clay. Hold the heat gun about six inches away from the fresh clay and keep the heat gun moving to avoid overheating the clay (it only takes about 30 seconds). Sometimes you can cover a moonie with the costume. Or, if there are many moonies, you could paint the entire sculpt with several layers of heat -set flesh colored paint, covering them up. No solution I know if really 'fixes' moonies.