Does epoxy have a shelf life? I just used some that I've had lying around for a good while and it's not going off 100% hard. It's bonded just fine, but is still a little "rubbery". It's fine for the fill-job I just did, but I'm wondering if I need to toss it and buy new next time I have something structural to do.

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H16 back in the day
SC17 right now
Bradenton, FL
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Yes, epoxy has a shelf life. Always a good idea to do a test batch before using old stuff. Assuming that you measured and mixed the batch properly and that the ambient temp was high enough during the cure cycle, I would say your resin is expired and should be tossed.

sm

Well poop - I have quite bit left. Yes, it was mixed right and I was working in 75 to 80 degrees. Luckily I was just gap filling with some cabosil mixed in so the softness actually worked to my advantage, but I'll have to dump what I have left.

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H16 back in the day
SC17 right now
Bradenton, FL
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FYI, this is from the FAQ from uscomposites.com regarding epoxy shelf life.

23. What is the shelf life of your epoxy systems?

We recommend using our epoxies within one year of purchase. Epoxies should never be stored in direct sunlight and should not be kept in freezing temperatures. Storage in temperature above 90 degrees should also be avoided.

You will find that your epoxy can last much longer than a year if they're kept in a dark storage container(cardboard box) with temperatures between 60 and 80 degrees.

If you sometimes have to wait a couple months in-between uses we recommend shaking up the hardener bottle for about 45 seconds to re-agitate any settling that may occur. This is not necessary for the resin.

sm

I had some epoxy , think it was system 3 that I used to glass a wood strip kayak, after sitting for a few years they told me to put the contaners in very hot water to soften the epoxy and then stir each contaner up before I used it, had very good results doing that . Like dogboy said also a small test batch would be a good idea . Also let it cool before you mix it or it can set to fast on you.
Jay

Interesting. It was stored per US Composites recommendations, but I definitely did not agitate the harder before I used it. I might mix up a small batch tomorrow to see if that helps.

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H16 back in the day
SC17 right now
Bradenton, FL
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I had some West system epoxy that I "inherited" after maybe five or six years from a guy who rebuilt a wooden Wayfarer. Nice boat. Anyway it wouldn't harden. With fresh hardener it worked fine. So my exhaustive testing (once) says that the epoxy has a long shelf life but the hardener has a much shorter life.

205, the Viagra of epoxies

I had some West system epoxy that I "inherited" after maybe five or six years from a guy who rebuilt a wooden Wayfarer. Nice boat. Anyway it wouldn't harden. With fresh hardener it worked fine. So my exhaustive testing (once) says that the epoxy has a long shelf life but the hardener has a much shorter life.

205, the Viagra of epoxies

Having used various brands over decades of building/tearing up things, I offer the following.
Sometimes, it depends on the materials being bonded. I know this sounds wrong, the stuff should kick no matter what it's on, but it doesn't.
Decades ago I discovered that brand new,(I don't know how long it was at the store) 3M Bondo does not cure when on latex gloves. I had thought I could re-use the same gloves the next day. Wrong, the fingers were all sticky. The repair I did,(floor panel on a Gran Torino) set up solid, but the resin on the gloves never did.
Last summer I attempted to repair a foam cored batten that showed some delamination, using newish epoxy. It never set, although the stir stick was rock hard, as was the remaining material in the mixing cup.
I'm quite sure the West System website states it has a long shelf life, but I cannot get any of their pages to open.
The Website for MAS Epoxy states;
"The stated shelf life is 1 year from ship date. However, our epoxy systems have been known to last much longer. You can prolong the life of your epoxy resin by following the best storage practices mention below. Or, if you find your product to be crystallized (solid or chunky) see details below on how to return the product to its liquid form."
"Crystallization is the separation of important chemical components of your epoxy resin and is characterized by resin that is solid, chunky or cloudy. Crystallization compromises the strength and finish of your project and for that reason crystallized resin should not be used until it has been liquefied. A crystallized resin or hardener can be returned to its original state by heating the material to 140°-150°F and stirring until it returns to the liquid state. Our customers have had success with re-constituting crystallized resin by putting the container in a hot bath in their home or using a black tarp in the sun to warm the bottle."

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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
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Thats the way mine was , kind of white and chunky, dont tell the wife but I put the contaner in her electric skiilet with an inch of water in it and heated it till it sofftened and mixed it up and it worked fine after that

No one took a shot at the title of this thread?

I have some West System epoxy and hardener. Good to hear I might get some more time out of it. I think I'll head to the garage and shake up the hardener.

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Tom
NACRA 5.7 (1984 Sail 181)
Pennsylvania
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tominpa

No one took a shot at the title of this thread?

I have some West System epoxy and hardener. Good to hear I might get some more time out of it. I think I'll head to the garage and shake up the hardener.

west system that is old will have a red hue - this doesn't effect the strength
west systems suggest you put resin in a hot bath to resolve any crystals that may have formed

The Website for West Systems is back up.
Scroll to bottom of page for useful life information....both resin & hardener, "many years"
http://www.westsystem.com…a-PDFs/TDS%20105_205.pdf

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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--

I use West System ALOT. Have a sail club with about 25 monohulls (mostly Sunfish) and about 8 cats.
I've become the resident repair guy.
I've noticed the same thing about it not setting up (on occasion) and initially chalked it up to poor mix amounts, but that's hard to do with West.
Mine stays in an unheated garage, and I do more repairs in winter than warm weather.
About two years ago I started bringing in the epoxy to a warm room prior to use and then stirring it up prior to use. Makes a world of difference and some of these epoxies have sat in garage for 2 plus years.
I do attempt to heat the garage for the actual repair, but not always ideal temp with my space heater use. I have to ventllate often when using acetone, paint, glass work, etc... As my space heater is a construction style torpedo.
Promised the wife that I would try not to burn the garage down.
Also found out that non-alcoholic beer will freeze easier in the garage fridge than real beer. That was an easy fix- no more NA beer.
Love the thread title.

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Supercat 15
Windrider 17
Several Sunfish and Sunfish clones
Ratboat built from Zuma and Sunfish parts
Shallow water sailor in the Delaware Bay
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tominpa

No one took a shot at the title of this thread?

I know, right? And I went to all that effort....

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H16 back in the day
SC17 right now
Bradenton, FL
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Haha, yeah, when I first saw the title I thought it might be about viagra!!!! Lol!!!

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Marty
1984 Hobie 16 Redline Yellow Nationals, "Yellow Fever"
Opelika, Al / Lake Martin
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Well it looks like mine will be able to get hard for a long time to come...

Thanks Ed for the link to the material spec.

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Tom
NACRA 5.7 (1984 Sail 181)
Pennsylvania
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