Hi everybody,

I searched the forum and already found some interesting threads about this theme but I have an additional question.
I already tried about 4 moulds with high epoxy temperature gelcoat (EM160 from EC) but every time I have some tiny pinholes on the surface as you may see in the photo on the right. I do not know where the mistake is but now I am going to try a repair instead of doing another mould. So I was wondering if it is possible to get away with the pinholes by using the S120 board sealer? Anyone with experience in this? I read a lot about using it to epoxy modelboard but I think this has no pinholes. After all I think the pinholes are too small to fill up with new epoxy and get a good key!?

The left picture shows the only one large hole in my mould. This is too big for S120 for sure, but do you think it is necessary to repair it after all because it is not on the surface of the finished part. Or will this hole steal too much resin from my prepreg so that there will be imperfections on the surface because of that? If I have to repair it with some additional gelcoat, will there be no problem becaus I cannot make a key on the surface!?

And my last question: The surface of the original part has a matt finish. But I want the carbon to be high gloss. So usually I would polish my mould. But what is when using the board sealer all over the mould? Would this be enough to get a high gloss if you follow the TDS and use about 5 layer, sand it with 1200 grit and put a final layer on?

Thanks a lot for your help guys!

The pinholes are trapped air.  The bigger ones should be easy to fill in.  The tiny ones you can sand back and recoat or try wiping over with gel to fill them.  Sanding back is usually more successful but more finishing work afterwards.

The gel being quite thick can be prone to air entrapment in some cases - eg lower working temperatures, thick coatings, aggressive mixing etc.  At warmer temps, the resin is thinner and traps less air.  Sometimes a thin surface brush coat can help get out bigger bubbles, then straight away go over with more gel to get your proper  thickness for that coat.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Thanks Warren!
Can you perhaps give me also some infos about my S120 board sealer questions?

You will unlikely fill big pinholes like that, more for surface fine porosity, dullness, fine scratches etc over the whole surface where a recoating all over would be beneficial.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

+x

 

Warren (Staff) - 5/2/2018 8:24:04 AM

You will unlikely fill big pinholes like that, more for surface fine porosity, dullness, fine scratches etc over the whole surface where a recoating all over would be beneficial.

What about this?

And my last question: The surface of the original part has a matt finish. But I want the carbon to be high gloss. So usually I would polish my mould. But what is when using the board sealer all over the mould? Would this be enough to get a high gloss if you follow the TDS and use about 5 layer, sand it with 1200 grit and put a final layer on?