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 Warren, I think we may have spoken earlier today.

I'll go over with the heat gun a few times see how if that makes a difference. I was thinking of the tape as a potential fix as well! I may do this just for peace of mind, even if it is a bit time consuming.

Just a question on the wax - can this be any car wax, or might they have additives that will cause issues? Only wax I have knocking around is the G3 Superpaste Wax, which is sort of a hard wax but not quite as it goes very soft immediately when touched. And if it is acceptable, it should be OK as long as it is applied on top of the easy lease?

I would stay away from unknown waxes. Composites can be a super unforgiving process, and they will bite you hard if things aren't right. Chemical incompatibilities is a big one, and there are loads of different chemicals out there - waxes included. While I know Carnauba based waxes are used in both release waxes and car waxes, there is no saying that there aren't other solvents or chemicals in there that will cause issues. Or perhaps a car wax may be too thin and not build enough to function well as a release agent. There are plenty of people who will argue with this and say they have had success using various waxes etc. All things considered, it is a risk. And if you have already binned a mould and this is make or break time, you don't want to be putting your faith in materials that are an unknown variable.

Your problem does sound a bit different to what I have experienced. I've never had patches go dull after cleaning, this does indicate that the surface isn't cured properly. For me, the mould visibly remains exactly the same, but I get some red coming off on the cloth I am using. I would suggest covered these dull areas is going to be a good idea, either with flash tape or with PVA release agent. Get a physical barrier in between, because there is something odd going on. Whatever you use - just keep away from the flange edges where your bagging tape needs to seal.