Originally Posted by Little Blue
Speaking one non expert to another, I find the subject confusing.
From what Ive been able to find out/summize I think the following is true.
Plastic Gelcoat filler is not gel coat, but does a good job of filling small areas of damge. Just overfill the damage let go off completely and then rub down flat with gradually finer weet & dry.
True gel coat is a liquid that sets by the action of a catalyst in the absence of air.
As its designed to be the first layer in a mould, air is excluded so it sets. If you use it in air as a top coat or filler, to get it to set you can add a special parafin wax this rises to the surface and protects it from air while it sets. I believe that the use of tape is just another way of excluding air that is sometimes used.
Gelcoat is usually white and manufacturers add pigments to get the coulours they want.
If anyones an expert and can add to this or correct me I would be interested to hear from you.
The only time you should be using tape over a repair is if the gelcoat wont stay in on its own, ie if the repair is upside down......
The additive is called styrene wax 4% solution, this leaves the repair in a non sticky state, gelcoat as you rightly pointed out is meant for a mould surface which is free of air, if no wax was added the repair would stay tacky to the touch.
if you want some gelcoat for a repair i can send you some 49PA ready mixed with 4% wax solution