Epoxy Mixing Technique

[Triton106]

I have been using System Three epoxy for a while now. I don't usually have large projects that require significant amount of epoxy. The times I need a large batch of epoxy I have been very frustrated by how quickly the resin heats up and solidify. It usually happens when I add West System thickener. It happened again today as I tried to build up the base for mounting the flue cap for the solid fuel heater. Before I even know it the resin started heat up and in attempting to salvage as much resin as I could I mixed in some resin that is already heating up and ended up with a hard chunk (about the size of a piece of peanuts) in the base. My questions are two fold:

1. How can I prevent the resin from heating up?
2. Is there any harm in leaving that small piece of resin in the base? There is not much stress on that part, the main purpose of the base is to create a level surface for mounting the flue cap.

Thanks in advance for your help.

[bcooke]

Use a bigger mixing bucket...

The more bunched up the epoxy is the faster it heats up which accelerates the curing. A larger - and more specifically wider- bucket will allow the epoxy to spread out and dissipate the heat better.

The other option is to complete the project in stages with manageable amounts of epoxy at a time.

Heat build up is inevitable and a part of the chemical reaction. There is a finite amount of epoxy you can apply before the heat buildup starts having adverse effects. You can't just apply a big concentrated pile of goop and not see it boil/ignite.

[mitiempo]

Agreed, a shallow tray is better than a deep mixing container. I use West and always use the slow hardener to get extra working time as well.

[avd155]

A general guide is that if the epoxy is kicking on you, you're mixing more than you can handle.

If you're doing a big layup, begin with smaller batches until you get rolling. Then, as the project progresses, make bigger and bigger batches as you get more comfortable with your project set-up and techniques. Temperature also plays a big role in how your epoxy is kicking (as well as direct sunlight). Maybe try working later in the evening or early in the morning to get the coolest temperatures you can. I've also heard that putting your epoxy in an ice chest with some ice on really hot days can give you more working time, but summer just started for us in the NW so I haven't yet had to give that one a try.

In the end, it's all just getting a feel for it and I bet if you have a few kick on you, you'll figure out how to stop that happening. Especially considering the price of the epoxy :)

[Ric in Richmond]

You haven't lived until you've wondered if that smoking cup is actually going to burst into flames.......

[Hirilondë]

I have actually set up my cans of resin and hardener in a tub of ice during the summer. It helps a little. The 3 best techniques are large shallow containers and workable size batches as mentioned above and spread it onto the work area ASAP. Once the epoxy is spread out the cure rate slows down a lot and you can work it as needed at a more leisurely pace.

[Triton106]

Thanks everyone, I think I did everything I am not supposed to do yesterday, including too small a container for the amount of resin I was mixing, weather was too hot, under direct sun... No wonder.

[Zach]

Use tropical hardener. You get almost an hour at 80 degrees. It is the only way you'll get a cabosil thickened fillet to stay put on a hundred degree day in the sun...

If you must use slow hardener, put the bucket in the shade... and off any asphalt around.

If you are doing a fiberglass layup, put the area you will be doing the glass, in the shade by rigging up a tarp.

Wet out the cloth, on a wet out bench. Take a piece of plywood, and staple some black plastic 2-4 mils thick to it (wrap around and staple the underside.)

Have the cloth pre-cut, and use a sharpie to mark the direction and layers of the install.

Mix your resin and wet it out. If you are doing a decent amount... say 4 feet square, of glass, use a paint roller. Just grab one of the cheapo green polyester rollers in the two pack at the hardware store.
Roll the cloth out, flip it over. Stack the next piece. roll it. Stack the next piece... roll it. Etc. When the glass goes clear it is wet. If it is white, it is dry. If it has a puddle of reisn on top, or goo is running off of it... you used to much. Roll out the excess.

Air roll it, now carry a chip brush over to the boat. Wet out where the glass is going with the paint roller, Touch up with the chip brush. Plop it down, and use a ribbed aluminum roller to work out the excess resin.

It depends what I am doing, whether or not I roll the air out of each layer on the bench, or carry a small board with the stack of gooey glass on it... flip it upside down and peel and stick each layer rolling as I go. If its less than a quart of resin, I just do it on the bench and be done.

If its a side deck or something, I'll roll the dry glass up and wet it out in place...

Take a squeedgee, and pull the excess resin off by sliding it over the top, and dumping it back in the mixing bucket. Wring out the paint roller with your gloved hand into the pot too. Go ahead and pull it off and chuck it, if you are done wetting out.

I mix microballoons into the excess resin, and even mix a little more if I have to to fill the weave of the glass on the top and save from having to sand off half the top layer of glass to get a smooth surface.

From there, drop the squeedgee and air roller in acetone, and wipe up any drips.

Zach