25% or more graphite by volume gives you all the UV protection that you need.

Laszlo

As Laszlo mentioned, the graphite provides the UV protection for the bottom, and yes, the slow cure will generate less heat.

If you are concerned with it "going off in the pot" consider mixing much smaller quantities, and get it out of the pot and onto the boat as quickly as you can. The "working time" will be a lot longer with the epoxy on the boat compared to still in the pot where there really isn't anything to disipate the heat,and the hotter it gets, the quicker it will start to gel and turn into a hockey puck.

Keith

Thanks for the answers.  I am not using graphite on the bottom, I was just wondering while I was hand sanding.  The temp question was in preparing for an end pour.  Another time when I used some West I had, It really heated up, which I expected, but it was hotter than I thought it would be.  Using slow hardener this time, logic told me it would generate less heat, but I wasn't sure.  The end pour on this boat generated very little heat, using MAAS. Launch day may be tomorrow if the final varnish coat feels hard enough to strap to the racks.