Pigmenting filled resins


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Hanaldo
Hanaldo
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Hey all,

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 have managed to get away with using that colour, but I would like to find out if it is possible for me to create my gelcoats with the solid black that I'm after. I don't want to add too much pigment obviously, and anything beyond 2% doesn't seem to do much regardless. So, how do proper tooling gelcoats like the Unimould system obtain such a nice black colour?
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brainfart
brainfart
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What kind of fillers do you add, and what kind of black pigment have you tried? And how do you incorporate these into the resin? Stirring by hand or with a machine?
Deep black is usually made with some kind of carbon black pigment. Obviously there are uncountable different commercial grades for many different applications available. If you buy black pigment pastes they are already diluted and you have no idea how much carbon is actually in there. Some might contain a lot and others just barely enough.
A common ingredient for gelcoats and other resin mixtures is fumed silica thixotropy agent. This will work when mixed in by hand, but much less is required when high-shear mixers are used. Much less means 80 or 90% less in this case! Other fillers might behave similarly. So you can reduce the amount of filler materials by extremely intense stirring. Less white fillers and properly dispersed pigment means darker colour.
This of course requires specialized equipment that is not available in your average hardware store.
GO

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