I have a new cedar strip build in progress - its an SUP, not a kayak. It's hollow, and requires the interior surfaces to be sealed, but not glassed. Although I have only ever used West System products before, I decided to try System Three S-1 sealer for this, as it is very low viscosity, which would make it much easier to brush on and absorb into the dry wood. So I read all the instructions and product info carefully, got set up with my ordinary plastic disposable containers, measured out one cup each of parts A and B, and then combined them into a third container, and then left it to stand for the prescribed 15 minutes. After 15 minutes, just as I was picking up the 2 cup mixture, I noticed that the bottom of the container seemed to be deformed, then the bottom of the container suddenly dissolved and fell away, and two cups of fresh epoxy spilled everywhere it shouldn't, leaving a huge mess on me, my project, some tools, and my workspace. In other words, a minor disaster. I subsequently contacted System Three customer/technical support, and have been having a very frustrating time with their support person. I suggested that the product instructions should include any cautions or restrictions on the use of plastic containers. (I also pointed out that the usage instructions as printed on the product differ significantly (temperature range) from the instructions on their web-site, but that's another story) I was pleased to get a quick response, and the explanation was that this was clearly an "exothermic" reaction, ie. that the mixed product was creating its own heat build-up, and simply melted the plastic container. Hmmm - that was unexpected. I am aware of exothermic reactions, and have noticed West epoxies do that in some situations, but not to this extreme. I then pointed out to him that I also noticed that one of the individual containers that I measured the separate parts into (the B part) also dissolved, even though it was not a mixture of the two parts. He responded again, and apologized for his earlier explanation, which was completely incorrect: S-1 sealer does not create an exothermic reaction at all, so it was simply that I was using "inappropriate" containers. He went on to say that if I want to use plastic containers, they must be PE (polyethylene) or PP (polypropylene). Of course, I don't really know what kind of plastic my disposable cups are made of, nor do any of these products generally say what they are, so that's not a great help. System Three sells its own plastic and paper mixing cups, but does not identify what they are made of. Again, I pointed out to him that it would be useful if this was mentioned on any of their product literature, but his response was that they "can't be exhaustive" with their label information, and that they provide "ample information" and that using this product requires a learning curve. I had also asked him some specific questions regarding cure time and re-coat time, as they may be affected by ambient temperatures, and he acknowledged that they are indeed affected by temperature, but simply refused to provide any further information, basically recommending trial and error. So my foray into using System Three has been less than wonderful. End of rant.