The Rot Doctor


Subject: L & L Resin (mixing with wood stain)
Date: Fri, 29 Oct 2004


I added wood flour and mahogany stain to equal parts of the subject resin to use a filler. The temperature has been in the low 70s during the day and 45-50 at night with above average humidity.

The mixture is not hardening. Why?




Incomplete mixing is probably the most common problem, but this usually shows up as spotty areas that don't cure. So I don't think that this could be your problem.

Temperature should not be an issue. Colder temperatures will slow down the cure, but properly mixed, the resin should cure in 2-4 days at the temperatures you are giving me. If it has only been 24 hours, I would wait and see if things are progressing. As long as it is curing, even if it is slowly, I would let it finish. Warming the mixture will accelerate the cure, but be careful not to heat it over 100 degrees F. Cold temperatures combined with not enough of the hardener can cause the mixture to not harden. But as long as you mixed equal parts or close to it, this should not be the problem.

Barring any of above issues, my guess would be that the mahogany stain may have disrupted the catalyzing process of the epoxy. There are specific epoxy resin dyes, which we sell, that can be used to tint epoxy resin. But even these should be used in small amounts. Too much will ruin the epoxy. When I need to put large amounts of pigment into the resin, I always use a dry pigment, not a liquid. Most dry pigments are inert, and will not interfere with the catalyzing of the epoxy. Was the mahogany stain a liquid? If so I would suspect that this was the problem.

If the mixture is curing very slowly, just let it finish. If the mixture just won't cure, then the only remedy is to remove it and start over. Be sure to use lacquer thinner to remove all the non-curing material. Even a thin layer of uncured epoxy will ruin the ability of the new epoxy to bond well to the surface.