I relearned a valuable lession last night while repairing some fiber glass on the back cap of the motor home. It is cold out here now, well cold for Phoenix anyway, and my epoxy was rather thick. I thought a bit in the microwave would thin it out for aplication right quick. I absent mindedly mixed up about a half oz and promptly ran in and popped it in the old nucker for 30 seconds. Yes sir e Bob that thined it out alright. Then promptly solidified it right in my hand. I had thoughtfully put the paper cup in a plastic one before starting this ill fated adventure in physics. I got the mess back into the garage before it started to off gas so she didn't catch me in the act. Ya know how you kind of chuckle and think what the hell was I doing ??? Well I went through that drill while I mixed another batch of cold poxy. 5 seconds was just right. 8) 8) 8)
;D
I'm not laughing at you - well, maybe with youÂ
Some sailors like to live dangerously.
i am laughing at youÂ
i will be at the tub this sat afternoon if you want to stop by. i am cutting some plywood to cover the four sides of the bulkhead then i will cover the boards for the bunks. I love making templates.
been there and done that. but i used a camper stove. i was not interested in crossing the rear admiral. i heated the seperate parts in their original containers in a tub of warm water. i found, like you did, that the warmer the goo, the faster it kicks. this trick is a must around here because i store my stuff in an unheated shed and the temps get below freezing around here at this time of year. if you don't warm the goo, it is thick as tar.
Epoxy can lose up to half it's strength if it cures in cold conditions. Warm the part. I've used heat guns to warm up parts to get cold epoxy to "flow" and also to get it to soak in better. Remove the heat before applying epoxy on raw wood, so that the wood is cooling. Even molasses like goo will quickly thin out and run like water on a 90 degree surface, literally within a minute.
Also epoxy can crystallize at freezing temperatures, which will prevent it from curing properly. All you need to do it warm it up, stir it good, then reseal the container if this happens.
Epoxy also has a shelf life of about a year in metal containers, a little longer in plastic or glass. I've used several year old epoxy, but never have tried it on a structural element, preferring to believe the test results from the formulators.
A Tupperware tub filled with warm tap water will usually bring epoxy up to temperature, within a half hour (depending of container size).
You have to be careful with hot epoxy, it'll kick quick. It's much better to have warm work, so the epoxy can warm up, flow out then cool. 90 degree epoxy (like the stuff most everyone uses) will kick as you're mixing it or very soon after. 80 degree goo will kick fairly quickly, but in small batches can be managed. I'm referring to West System 205, or regular System Three or Raka's regular resins. The average slow hardeners will tolerate 80 degree temperatures fairly well, but not for long if in the upper 80's. Some companies (West System 209 for example) will tolerate mid 90's well, but can't even cure unless the temperature is in the 70's or high 60's.
Use a thermometer and bring the epoxy up to the mid to high 70's and warm up the work to the high 70's low 80's and it'll flow like water and cure normally.
You also can "post cure" the epoxy. That is put it on, regardless of temperature (be reasonable) then warm up the work to 100 or more (120 is best for regular epoxy). It'll kick fast and cure extra hard, but runs, sags and drips are more of a problem with the extra thin goo.
I am working on the back bumper (ya right bumper) of the RV. It has been broken three or four times and now I have rebroken the lousey fix that it had. (Bondo) I backed the holes and cracks with glass cloth on the inside and am filling the gaps from the outside and will fair and paint. The thickened stuff from last weekend never cured except the first couple thousands of an inch on the outside. I scraped it all out, added a bit more glass yesterday. This week is supposed to be in the 70s at quitting time so maybe it will work better. I may have done a poor wag on the mixture as well. Small batches of 2:1 can be eyeballed very well if you always use the same cups but after not using it for a while the eye looses some of its fine resolution. As couple batches is all it takes to recalibrate. Bigger batches are another story.
I've repaired those "urethane" style of bumpers before, the last a Camaro I had. To make it work better (stay stuck), use cloth on the inside with the plastic very roughed up (24 grit), because the epoxy doesn't stick well to this stuff, so use several inches of "tabbing". When filling it (outside) use milled fibers in the mix as a first coat (fill it low, but bridge the gaps). It will increase the adhesion and strength of the bond. Follow with a light fairing coat to provide something to sand down flush.