Too Much Epoxy, Too Much Heat
I mixed too much epoxy at once and watched the exothermic reaction turn it into a smoking block, melting the plastic spatula. For bigger jobs, I’ve learned that less at a time is definitely better.
Here is a cautionary tale about mixing too much epoxy at once. What you see is an effect of the way an epoxy resin hardens.
In short, because this reaction is exothermic- heat producing - when resin/hardener mix starts to harden it gets warmer. More mix, more heat produced at once. And since the mix hardens much faster in higher temperatures- well, if there is enough mix, it creates so much heat that at some point - quite suddenly and violently- chain reaction starts.
Mix gets hotter, so it hardens faster, which produces even more heat, which speeds up the reaction... and da capo al fine.... All of these in about 1 second. And you have hot (sometimes it can actually start a fire!) smoking bloc of hardened epoxy. And melted quite thick plastics (spatula is a standard West System one, quite tough little things...).
And what is too much of the mix? Well, in this case it was around 20 pumps. Some of this amount was poured into a tray for a roller so what’s left is about 13-14 pumps. And about 20 minutes. That’s all.
So if you do some bigger jobs - less at one time is better. I have used so far up to 12 pumps without problems, never tried more to avoid such a result 🙂
