Microwave Epoxy set in the bottle?

I had a set of bottles of 6 minute epoxy where the resin portion actually took a partial set n the bottle and turned thick and cloudy.
It was not contaminated with hardener. Someone told me that it could be retored by putting it in the microwave until the coudiness disappeared.
Anyone know if this is true?
Joe
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If we're lucky, one of the materials engineers will check in and answer your question.
In the meantime, one thing I know is that heated epoxy gets runny but then sets quickly.
I would expect that you could get the unmixed resin to heat up and flow more easily. Whether it will all become good as new is beyond my ken.
I wouldn't microwave it myself. I'd go for immersing the bottle in hot water. That seems to me to be the safest way to get some heat into it.
                Marty
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This is almost like asking how much mold on your two week old hoagie (sandwich) is acceptable and at what point do you throw it away. 1/4", 1/2"?
When the epoxy gets that old, it will form a weaker and perhaps unacceptable bond. There comes a time when the epoxy should be replaced with new epoxy. The OP has reached this point.
Ed Cregger
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I have some 20 min epoxy which has thickened in the same way - I just warm it up in a cup of hot water and then let it cool - it stays runny for a few weeks. Does not seem to affect the cure at all.
--
Phil Olson


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You can always count on Ed to answer a question where he has zero knowledge. You can also always count in him to be dead wrong.
Epoxy are sold as supersaturated solutions. They are so viscous that crystallization is slow unless somehow they happen to get seeded with something which will serve as a crystal nucleus. Same exact story as the honey you eat. It will store and stay liquid for months or even years if never opened and not disturbed. But sooner or later it will crystallize. Has the honey spoiled? Not at all. Just heat in in a microwave and it will go right back into solution.
But microwaves are tuned to the water frequency. And honey has quite a bit of water in it to soak up the microwaves. Epoxy does not have water in it unless you put some in there. If you put water in it throw it out and buy some new stuff.
But if you have not contaminated it somehow it is perfectly ok. I keep mine in my shop which goes down to 45 deg when I am not there and the epoxy is usually crystallized when I go to use it. I just heat the bottle over a kerosene heater while rotating it constantly until it goes back into solution and it is good as new. Epoxy does not wear out from age. Well, maybe in a million years it might suffer a bit unless very carefully sealed.
A pot of hot water would work fine to redissolve the solids also but would not be as fast. Make sure you recool it before use or it will kick much faster then you probably want it to kick. Not a thing wrong with it and anyone who tells you to pitch it is simply ignorant. Its physical properties will not be damaged even a little by crystallization as long as you make sure to redissolve before use.
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| But microwaves are tuned to the water frequency.
That is a common misconception. Microwave ovens are generally tuned to a frequency right in the middle of the 2.4 GHz ISM band, yes, but there's nothing special about exactly 2.45 GHz with regard to water.
Yes, 2.45 GHz radio waves are absorbed by water, but higher frequencies are absorbed even better. 2.45 GHz is not a `water frequency' (not any more than any frequency from 2-1000 GHz, anyways) or an absorption peak or anything like that. Basically, it's a compromise between `not being absorbed enough' and `being absorbed too quickly'. That, and the FCC (and the equivalents in other countries) have allocated this band for this sort of use.
Pretty much any frequency from 0.9 GHz to 10 GHz would probably work OK for a microwave. Even higher frequencies would work, but your food wouldn't be cooked very deeply (as it would all be absorbed by the outer layer of the food.)
Industrial microwaves often work at 915 MHz -- the middle of another ISM band. The lower frequency is not absorbed by water as well as 2.4 GHz is, so it ought to be able to cook larger items more deeply than a 2.4 GHz microwave oven could.
| Epoxy does not have water in it unless you put some in there.
Right. I've no idea how well epoxy would absorb microwaves -- probably not well. The idea to heat it up in a glass of hot water is a good one.
--
Doug McLaren, snipped-for-privacy@frenzied.us
They say only the good die young. If it works the other way, I'm immortal.
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On Jun 27, 12:25 am, "Doug McLaren" <dougmc

You are correct that water has a very, very wide and strong absorption band. But most organics absorb very poorly at the frequency used in microwave ovens. Just do a simple test. Put a cup of water and a cup of cooking oil in your kitchen nuke. Run the nuc until the water is boiling. Now check the temp of the oil. It will be barely warmer then when you put it in.
I would expect epoxy to behave much more like oil then water in a kitchen microwave as chemically the bonds in the epoxy are much like those in cooking oil and not at all like those in water. If you used the right frequency I am sure you could heat either oil or epoxy just fine in a microwave but the commercial units are not tuned to those frequencys.
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Doug McLaren wrote:

I have heated epoxy in the microwave many times and it heats faster than water. Never a problem with putting the bottle in the microwave.
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"One test is worth ten thousand expert opinions."
I'm not going to run that test myself, but I appreciate your courage and your field report. :o)
                Marty
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----------------
I do have a friend that spent twenty years building a two masted, gaff rigged schooner (30' length) utilizing the West Systems epoxy and fiberglass over wood (mahogany) technique. I helped him a tiny bit here and there, but mostly we discussed using epoxy and its implications over the years. He kept me abreast of the latest developments in epoxy technology. While I am not an engineer and do not pretend to be, I know a little something about epoxy.
The Gougeon Bros. (sp?), sellers of the West System, made it very clear that their epoxy, and that of the majority of other vendors, is only at engineering spec for a period of 18 months after manufacture. My friend, being the engineer that he is, confirmed this information in several ways. As a result of his confirmation, I often ended up with more expired epoxy, or soon to expire epoxy, than I could use at any given time.
So, with that said, and known to be a fact - nah, I won't say it.
You know, junior, it is okay to have differing opinions, but it really makes you look like an idiot when you insult others without provocation.
Ed Cregger
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It is really nice to know that someone as fully stupid as you are can survive in this world. I have known a lot of sales people. I have done a good bit of sales myself. It is a great way to make a living, particularly if you want to make a six figure plus salary. The smart ones do that with ease. The dumb ones like you who are always wrong manage to struggle along and survive. It is nice you survive as I do not want to have to feed you.
Being off engineering specs in 18 months was written by the lawyers to protect the company and has nothing at all to do with usabiltiy or performance of the product. Time limits like this protect against people who misuse and misstore the product. In the drug arena two years shelf life is the absolute limit. If it is a drug product even sodium chloride would have a two year shelf life on the label.
If the product is stored at such a low temp it crystallizes that will extend its shelf life dramatically. Solids are usually much more stable then solutions. I have tested many epoxys way older then 18 months, in some cases past ten years, and never seen measurable degradation in physical properties of the cured products if they were stored and mixed correctly. Almost no one ever mixes them properly. This is very true of the West System product line due to the high viscosity of their products. They are very difficult to properly mix.
In short I speak from experimental data on things like tensil strengths and moduli. You speak based on zero technical data, just opinion, hearsay and advertisement meant to sell more product. So stuff it little boy.
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wrote

--------------
Now I remember you. You are one of those technical people that envies the incomes of we sales people, as though it is our fault that you made a poor career choice. Have a good day. <G>
Ed Cregger
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Yeah, I was one of those technical types. And I made sure that the sales guys who were part of my organization, only several steps down the ladder from me, made six figures or I fired them. If they were not that good they were not worth keeping. In the organization I ran several steps down the ladder means I made a lot more money in salary then they made. If one of them was good enough to earn comissions that pushed my salary we were making so much money I simply got a lot bigger bonus. So the more the sales guys made the happier I was.
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wrote in message

Yeah, yeah! We sales guys can recognize both bragging and bullcrap when we hear it, Sunshine.
Can we get back to RC airplanes?
Harlan
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So the more the sales guys made the happier I was.
I'm just glad you were ever happy. mk

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Joe Nobody wrote:

I'm not sure if this would work or not. Maybe you could try it and tell us whether your airplane crashes, and then we'll all know.
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It helps thin honey that starts to crystalize in the bottle.
If you're letting your epoxy get that old, you're probably not crashing enough!

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Thick glutinous gunge tends to form pockets of vapour that cant escape until it actually reaches a pressure where it can force its way out in a microwave, the usual effect is a big 'BLUPP!' and the stuff flies everywhere and explaining why the innards of a microwave is coated with gungy Epoxy resin takes some explaining to the missus,
regards, Terry
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Joe Nobody wrote:

Do the following math exercise:
Add the cost of the kit you're building, plus the time you'll take to build it times what you make per hour (divide by two or three to account for taxes and the fact that you like building, don't forget that even if you're retired your time is still worth something), add in the cost of the radio.
Now divide that by the cost of a new batch of glue.
And ask yourself if you want to mess around with trying to revive old, questionable glue.
Finally: remember that there's economy, there's false economy, and they aren't the same thing.
--

Tim Wescott
Wescott Design Services
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I'd mess around with it for the kinds of things that I do with 6-minute epoxy (not too danged many; I never buy the stuff but I have picked up some as a fun-fly prize).
It would only take an hour to run the experiment with the hot water and a test joint.
At the end of the hour, I would know something new about working with epoxies.
"One observation is worth 10,000 expert opinions."
At the end of the hour, I would have clarity and peace of mind. Either the glue would prove serviceable or it wouldn't. I would only lose the time I spent on the experiment and, regardless of the outcome, I would know something afterward that I didn't know before.
                Marty
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