Epoxy question...

Re: Epoxy question...

John K Jordan

I don't have experience with epoxy like that but for finishes and chemicals in general I like to replace the air in the container with nitrogen before sealing. Argon is good too. This has preserved a variety of opened containers of finish for years, things such as TruOil which I've otherwise had set up in a few months. The gas keeps out both the oxygen and the moisture. I keep a tank in the shop.

I wonder if this would help with your (next) supply of epoxy resin.

Searching for 'epoxy shelf life' gave me plenty to read, for example:

https://www.westsystem.com/the-105-system/storage-shelf-life/

https://www.epoxyworks.com/index.php/epoxy-shelf-life/

https://www.prosetepoxy.com/home/shelf-life-storage/

Skimming these made me wonder what is different in the Chemcraft epoxy you bought. I didn't find out with a google search. Could it have been affected by something in your chemical cabinet?

I know people who have contacted one of the major epoxy companies such as West System for recommendations and help.

JKJ

Re: Epoxy question...

David Weaver

One good way to find out what happens. I have a different brand of epoxy like that but it's still clear. It takes so long to harden that it's not that convenient.

It crystalized.

Bill Tindall, E.Tn.

heat it up to melt crystals. next time buy West Systems

Thanks, John, David and Bill...

Barry Irby

John, you are right, plenty to read.

David, it is hateful in that it is so slow. I understand that the cure rate is very slow to avoid over heating the mix. I hear some of them will boil and fracture, but I am too old to wait a week and in my tiny shop, I can't do anything else while waiting.

And thanks Bill, I suspected something like that but did not think it was that simple. I am making do with a quart of System 3 I had. Will replace it with West System.

hot epoxy

John K Jordan

>>> I hear some of them will boil and fracture

So true about the possibility of an exothermic reaction. Almost 50 years ago I ran a small metallography lab and potted 100s of sections of nuclear research reactor element plates for examination under a microscope. Twice I had a quantity of epoxy overheat, turn brown, crack, and "let the smoke out." Small volumes of epoxy, no problems.

The possibility of and fix for crystallization is discussed in the third web link I provided.

JKJ

Re: hot epoxy

Barry Irby

Thanks again. Now to figure out how to hold it at 125 degrees for 8 hours???

I knew I should not have given my Sous Vide to my son.

Re: Thoxiotropic answer

TomD

If it just needs heating, to get rid of chrystals, that is usually no problem. If it set up, and you used graphite powder, I would be surprised if you have future trouble.

You don't like it though, So I would buy some new stuff. Use up the stuff you have around the shop I am in Canada, and when possible I get my stuff in the US. WEST is premium, but one of it's key features, that it dries very hard, is designed to make it work structurally with and carbon fiber, hardly the kind of feature that is necessary (won't do any harm) with patches. RAKA is excellent, from the gallons of it I have used, but MAS, System 3, all make good products.

By the way, since you are using black dye/graphite in your mix, any small change in transparency is not going to be noticeable. You need a thixotropic agent if your epoxy is dripping all over the floor on you. Typically a product called coloidal silica or cabosil is the best one. Not very expensive. It will turn your clear into apple sauce, peanut butter, whatever you want. And unlike bodying with other fillers, the epoxy can't drain out. You can add structure to epoxy with stuff like sawdust, glass fiber, microballoon, whatever, but without some cabosil your epoxy can drain out.

Cabosil/coloidal tends to reduce yield. It can't shrink epoxy yield, but if you were filling really large voids you an mix cab 1-3 with microballoons and get a lot more yield out of it, and reduce weight.

I was looking for microballoons up here, turns out they use it in explosives, in mining (as well as makeup, and postit notes). If you mix the balloons with a powdered explosive it changes the profile of the explosion which is good in mining.

Re: hot epoxy

TomD

When I was building my trimaran, there were some huge fillets of epoxy, the largest by far was in the keel, but we also did a big one in the bow. In that position, with heat rising, it got so hot it smoked, and it looked to catch on fire. The only thing that stopped it that we had on hand was compressed air. That cooled it down, and the actual period of risk was short lived. I guess we had water in the bathroom, but that would have meant leaving the boat, and we didn't want to use water. I don't remember thinking of water. Still waiting for the lung cancer to pop up.

holding temperature

John K Jordan

>>> Now to figure out how to hold it at 125 degrees for 8 hours???

I keep an old toaster oven in the shop. I monitor the temperature with an inexpensive thermocouple reader:

https://www.amazon.com/gp/product/B001EUB6BM

I use this for things like "recharging" desiccant and measuring absolute moisture content of a wood sample with the Oven Dry method. Having a dual-channel thermocouple reader has been handy for other things as well.

I watch the temperature reading as the toaster oven heats up and adjust the dial to get the temperature I want. After setting it usually stays stable for extended periods but I do check and adjust periodically if needed.

You could also use the method I use for warming honey that has crystallized. Too much heat can damage the honey. I heat water in a large pot to the desired temperature on the kitchen range, turn off the burner and put the bottles of honey in the water, put a lid on the top and an insulating towel over the top. It will cool down slowly so more hot water will need to be added for such an extended period. Setting the pan on a suitable heating pad might also help. I'm guessing the temperature for the epoxy treatment would not be critical.

JKJ

Re: holding temperature

Barry Irby

I have a controller I cobbled together to turn a Crock Pot into a sous vide. It was set for 125 degrees (I think), to cook a steak to rare. Worked well. My son borrowed it after scoffing at it. His chef friend thought it was really clever. Then it was worthy of borrowing. He brought it back but that does not mean its functional anymore.

The company that sold me the epoxy agreed today to replace it, free. They thought it would be fine to heat it and use it, but agreed with me that it was foolish to use it on a really nice (I hope) table. I will try it on something I can throw away. Charcuterie boards anyone?