I had an informative exchange with System Three's support folks today, which might be useful to others as well.
I submitted the following question:
What is the official S3 opinion on the use of propane heaters around fiberglass and epoxy work? The epoxy book does not seem to address this. I have read definitive opinions to the effect that kerosene and fuel-oil heaters are definitely bad. Opinions on propane seem to be divided, based on my casual internet surfing. But I have read that propane is a clean burning fuel, so what's the official scoop?
Twenty-five minutes later (wow! talk about customer service) I got the following reply:
On Mon, Mar 05, 2007 at 2:25pm Technical Support wrote:
Heating with LPG or kerosene:
The combustion by-products of LP gas are carbon dioxide and water. These combine to form carbonic acid, which will react with the amines present inthe epoxy hardener. The net result is that more blush will form. Blush, in and of itself is not usually harmful. Direct kerosene heat is different in that unburnt hydrocarbons are also present. These made combine with the curing epoxy to form a surface that is difficult to recoat or bond to unless vigorously sanded. We never recommend the use of kerosene as a direct-fired heat source. Indirect fired heaters (using a heat exchanger) are acceptable with either fuel. If your only heat source is propane then we recommend that the area be heated well in advance of any epoxy coating or fiberglassing, the room be quickly ventilated prior to using the epoxy for this application and the heat be turned off when the epoxy coating or fiberglassing cures. It may be turned back on when the epoxy is non-tacky to a medium touch. The above does not apply to bonding as very little epoxy would be exposed to the air in the room.
I had one other question for them:
One followup question: do the precautions you outline below also apply when working with a "no-blush" system, ie, your Silver Tip Resin?
To which they laconically replied:
(Direct-fired propane can cause blush? That's it?? What the heck was I worried about? :))
On Sunday when I laminated the float half, I followed their suggested procedure almost to the letter. Mainly because if I had had the burner on while I was laminating, the fumes would have just about killed me (something stinks while that thing is running - maybe it's the excess carbon dioxide). I did turn the burner on a bit too early according to S3, but I checked the laminate for blush before doing the bulkheads tonight and it felt fine. It's something I'll be careful about in future.