Due to a lack of any available epoxy tooling gelcoats where I live, I have started making my own using laminating resin and a variety of fillers and additives. I like to add a black pigment, as the black makes it really easy to find low spots and polish to a great shine, however my issue is that most of the fillers I use are a white powder, so instead of a nice solid black gelcoat I end up with a sort of gunmetal grey. 

I am going to try adding some graphite powder into my next batch, this might give me a darker colour. Unfortunately I guess it just might not be possible to achieve a solid black when mixing my own gelcoats like this, though I'd be interested to hear what additives are used in professional gelcoats to give these properties without making them grey.