I found these answers on the following website. It was a boat repair site but they covered the wax issue to my understanding. I'm not a expert or even a novice in fiberglassing so I hope this helps. According to the answers, if you are using a mold, use "no wax" type gelcoat and if you are puting it on top of your project, use "wax" type gelcoat in your final coat only.
::LAMBOJim
http://www.thehulltruth.com/boating-forum/306004-wax-no-wax-gel-coat.htmlResponse #1:
Gel coat with No wax is usually used in a mold. The first coat is a non wax gelcoat. If it had wax then the next coat of resin and mat would not bond properly. I would say that 95% of repairs of gelcoat are with wax additive. Why? Because you are bonding to the repair surface and as it cures the wax rises to the surface and gives it a hard surface you can sand and polish. with out wax a repair usually is tacky on surface even though it is cured under neath. Some people doing repairs spray PVA over the gelcoat or tape wax paper to the surface. Both by removing air contact to no wax gel coat promote hardness. I hope this helps.
Response #2:
Gelcoat will not harden if it is exposed to the air, the wax rises to the surface and seals it during the curing process. No Wax is a good choice if you are laying up multiple coats, you don't have to remove the wax between coats. If you can seal the repair by placing a sheet of mylar or wax paper over the patch then the no-wax will work but if you can't you need to have the wax in the gelcoat to get it to cure. When I buy Gelcoat I normally get the no-wax varity and then get some of the wax additive so that I can make my choice when mixing up for the patch.
