Talk Composites - The Forum for Advanced Composites

Translucent pigment compatibility

http://www.talkcomposites.com/Topic25064.aspx

By GreyArea - 1/28/2018 1:30:14 PM

I just noticed your pigment bottles say “polyester/polyurethane” on them. Are they also suitable for your clear cast epoxy?
By Warren (Staff) - 1/31/2018 9:23:22 AM

Depends on the curing temperature but it should be hard.  If it has a tacky finish then that would suggest it was not accurately measured out or mixed enough.  Small batches of any resin can be problematic as for epoxies to cure properly you need ideally to be within a couple of % accuracy which is a challenge for many scales.  Also at that size, the waste on the side of the cup and the corner in the bottom of the cup can be proportionality enough to screw up the overall mix ratio and hence despite best efforts you can end up with a mix that doesn't cure properly.  We tend to recommend that using a bigger batch, eg 100g or more then accepting a bit of waste is the better solution as you are more likely to get a good cure.

You might be able to salvage it by putting the mould somewhere nice and hot like on top of a radiator or in an airing cupboard for a few hours as the heat may be enough to finish it off.