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Guest
Thu 29 Jul, 2010 18:14

Re: Questions From Menorca, Spain
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Regarding cracks forming in TB's due to excessive heat, you can simply do what I do.  Back down to about half to 2/3 what the recommended amount of hardener is and move the trays to somewhere thats as cool as you can get them in the hot winter months.  Even just putting them right on a cement floor (like in a garage) is better than on a table as the floor, which is lying on ground, will be cooler.  As a general rule 10 drops/liquid US oz is whats recommended though consult your data sheet or the back of the can for the recommended amount in case the resin you have has been formulated differently.

I routinely use about 6 drops/oz and the TB's still cure in about 2-3 hours, still shrink some and still fall out of the mold.

One time when it was cooler out I had a tray of them I'd poured which didn't seem to be curing after several hours so I left it on the outside porch all night (again made with about 6 drops of hardener/oz) and the next morning they were cured, fell out of the tray without issue and had no cracks.

As the temperature outside drops you can use more hardener to get the TB's to cure in a reasonable time if you're noticing your TB's are taking too long to cure.  In this situation, moving back up to the recommended amount of hardener or even a bit more (range is about 5-15 drops/oz as a general rule - consult the data for the particular resin you have though to be sure) most likely will not cause cracks so long as you don't move the pieces into heated space before they're fully cured.

I found a simpler solution which seems to work nicely.  Pour the tray of TB's and place it in a small cardboard box with lid thats only slightly bigger than the tray and about twice as high.  In the short term, if shielded from the wind you'd be amazed how insulating a cardboard box is.  Soon as the resin starts to heat up, the temp builds quickly in the box and they cure rapidly regardless the outside temperature (I've only tried this down to about freezing so there may be a lower limit I haven't hit yet).

Gene