Hi all,

I have a bit of a head scratcher that I am not sure what to do about. I have made a mould for vacuum infusion, using the uni-mould system with standard Correx fluted signboard to form the flanges. I am now coming to the final cleanup before putting down the Easy Lease release agent, but when I pass over the flange areas where the Correx was with the Easy-lease mould cleaner it constantly picks up something black from the surface (I am presuming the gelcoat as these areas had nothing else on them) and continues to do so over multiple passes.

I can only assume that the mould cleaner is attacking and dissolving the gelcoat, as there is a bit of 'grab' after passing over it, but it only happens in the areas of Correx. There is no issue with the areas on the part itself, or the areas of flashtape covering joins in the Correx. The gelcoat was all done in one go so it is the same ratio mix of catalyst/gel-coat as for the areas that have no issue, therefore it isn't a case of under catalysed areas of gelcoat. It is on all Correx areas, and only Correx areas; adjacent areas on flashtape are fine so that rules out undermixing as well.  The gelcoat had at least 48 hrs curing before demoulding and was catalysed at around 1.5% - plus as the other areas are fine I don't think there have been issues in the process.

Any ideas why this is happening? 

This is the second mould after the first was ruined during demoulding of the carbon infusion. I remember with the first mould cleaning up the Correx areas and getting the same result. At the time I put it down to residue from the black tape covering the flange joins I used (so I made sure to just use flashtape this time), and a conversation with Easy Composites technical support confirmed there shouldn't be any issues with the mould cleaner and the gelcoat so I proceeded.  I had some issues with the Easy-lease release agent where I made a mistake and it got contaminated with an application of wax I had used to get a good shine to the finished mould surface, so I didn't get a good release and some areas of carbon stuck to the mould and vice versa. However, the areas that were worst affected were the flanges where I hadn't applied any wax, just the easy-lease and it had pulled a good deal of the gel coat straight off the mould.

With the gel-coat being air inhibited my thoughts are that the Correx is somehow breathable and has not allowed the gelcoat to harden on the surface both times meaning it still has a tack and has bonded with the epoxy/or interfered with the easy-lease. Surely this can't be the case though as this is the recommended procedure? And if that is the case, what can I do about it? I fear that the I am going to get the same result as the first mould if I proceed...

Any help would be much appreciated!

Thanks for your help, interesting that you have had the same. I take it the compound in clean>compound>clean is a polishing compound?

I spoke to EC technical help as well and their thoughts were that the Correx had slightly delaminated early allowing air in contact with the surface, which make sense but I did have the gel coat on for 24 hours before the coupling coat so not sure if it could have delaminated with just the gel-coat? 

Also on further inspection it only has a tack after passing over with the mould cleaner, when dry it is ostensibly hard to the touch so I don't know. Their recommendation was to keep cleaning until stuff stops coming off and is no longer tacky, or apply a bit of heat to try and finalise the cure, and as an alternative if still no luck I could apply wax over the easy-lease on the flanges. After going over with the mould cleaner there is a mottled sort of finish to the gel-coat with completely matte areas and others a bit shinier so I wonder if the matte areas are where the solvent has removed all there is to remove - but that said after a good 10 mins of concentrating on a single area I'm still getting a bit of black on the towel. Only on the application cloth though - nothing comes off on the dry cloth when I wipe off the solvent so it must be a very minor amount.

I did the tape test as you suggested on a small area with just a single coat of easy lease and there was a very noticeable difference so that seems to suggest things are OK. I will do a few more passes with the mould cleaner to get it as good as I can without spending forever on it and stick with the process. I am a bit reluctant to add wax over the easy lease after the issues I had last time though - I really want to avoid destroying another mould as I don't have the time (effort or money!) to do a third!