I am having a problem with GC50 and shrinkage.
I've noticed shrinkage before in sharp right -angled corners, where the gelcoat has pulled away and out from the corner, often following one surface or the other leaving a void one side. Sometimes a bigger void one side and a smaller the other.

This time I have seen a fairly large shrinkage, shown below. I gave a thicker than normal coat of Sprayed GC50, with 15% white Polyester pigment, 3% styrene 2.5% MEKP
This piece is scrap obviously, and I've had to strip it out and start again.

I am using a gravity fed spraygun, with a 1.8mm nozzle. It's not a gel coat specific gun but does the job for me as the part is not huge. I would have thought that the gel coat gun would have provided a thicker layer anyway?

The mould is very well seasoned now, and I use TR regular wax only.

Any thoughts? This is probably the one problem I have with GC50, in all other aspects it suits me perfectly. I'd like to get on top of this, otherwise it's back yet agin to finding a epoxy compatible poletser gel coat!

You can't use multiple coats of GC50 as it has been specially formulated for epoxy to bond to it, so when you apply a second coat, it does not bond well to the first meaning you are likely to get delamination.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Aaargh! Getting into a corner again!

It's a real shame as GC50 seems very useful on the whole.

Pro's
It's sprayable
very polishable to a high gloss
Takes pigment well
UV resistant
Tough finish
Cheap

Con's
Shrinks where thickness not even?
Seems to not cure when in very thin layers
Pain to clean up the gun

I have tried many versions of epoxy gel coats. They all seem to get problematical when you want to pigment them, and seem to be on the soft scratchable side when cured?