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I have some left over West System epoxy resin and 207 clear hardener. They have been sitting in my garage for nearly seven years.

They might have been exposed to below zero centigrade a few days every winter. Are they still usable or have they gone beyond their shelf life?

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West Systems says the shelf life is practically unlimited. I’ve used stuff as old as 10 years and it kicked off just fine. If it has been super cold there may be some crystals formed. If so, just warm it up to ~50C (125F) and hold it there until the crystals dissolve. 

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I've used lots of years old epoxy with nary a problem.

Some of the resin has crystallized heavily but simply letting it sit in warm water re-liquefies it.

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I'll third that - it's probably fine once you warm it to re-liquify.

They do tend to darken with age - may be a concern if you're using the special clear hardener for it's clear color.

Worth mixing up a test batch before using it on anything important.

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2 hours ago, Omer said:

I have some left over West System epoxy resin and 207 clear hardener. They have been sitting in my garage for nearly seven years.

They might have been exposed to below zero centigrade a few days every winter. Are they still usable or have they gone beyond their shelf life?

Seems to last a long , long time 

if it’s uncontaminated use it 

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Colored hardener is from moisture absorption. I use it for small jobs, but would buy new for any large structural laminate.

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Test a small Batch

 

I have had and used many types and brands of very old epoxy. The oldest used to be some Marine Tex from the sixties we used in the nineties but I am certain I have some forty year old stuff somewhere in my shop. 
 

we have ALWAYS test first since we had our first failure. 
our first failure:

My old Buddy Jim and I hosted a gathering of all the local bist. Usiness folks where chemists and salesmen from Interlux came to town and demonstrated the new 2000 epoxy. Everybody got a complimentary  quart kit.

A few years ago Jim, whose eyesight is mostly gone, gave me his stash of Boat repair materials. He still had his complimentary quart of 2000 from the eighties. 
I decided to use it . It didn’t cure. After a week of waiting I scraped it off and rinsed away most of the rest of it and sanded the surface again before applying new material.

 

the only other old epoxy failure I have had was vc teflon primer epoxy  since renamed Vc performance epoxy. The catalyst turned to a solid rubbery can shaped solid. 
I tried carving a ball to see how well it bounced and the ball simply broke when I  dropped it. 

 

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18 hours ago, Gouvernail said:

Test a small Batch

 

I have had and used many types and brands of very old epoxy. The oldest used to be some Marine Tex from the sixties we used in the nineties but I am certain I have some forty year old stuff somewhere in my shop. 
 

we have ALWAYS test first since we had our first failure. 
our first failure:

My old Buddy Jim and I hosted a gathering of all the local bist. Usiness folks where chemists and salesmen from Interlux came to town and demonstrated the new 2000 epoxy. Everybody got a complimentary  quart kit.

A few years ago Jim, whose eyesight is mostly gone, gave me his stash of Boat repair materials. He still had his complimentary quart of 2000 from the eighties. 
I decided to use it . It didn’t cure. After a week of waiting I scraped it off and rinsed away most of the rest of it and sanded the surface again before applying new material.

 

the only other old epoxy failure I have had was vc teflon primer epoxy  since renamed Vc performance epoxy. The catalyst turned to a solid rubbery can shaped solid. 
I tried carving a ball to see how well it bounced and the ball simply broke when I  dropped it. 

 

Spot on

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The west hardener gets dark after a while and the final product will be yellow brown. If you are covering it NP but it looks really ugly compared to new stuff. 

The resin is basically unlimited. Warm it up and should be good. 

However testing is also good to ensure it kicks properly

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I found the brown hardener really realistic, to model a Highland peat coloured lochan.

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I used some 3 year old West 205 (fast hardener) recently that had been sometimes left on the boat in heat and cold (up to 95' and down to 25'F) during boat work.  It was a bit darker than normal, and it kicked really slowly in 68' temps, indoors - 5-6 hours to kick to a little tacky (should have been 60-90 minutes, tops), 18 - 24 to cure to non-sticky hardness (should have been 6 hours).  I used it in non-critical applications where the epoxy was an additional level of adhesive coupled with screws (joining flat mahogany chunks to form blocks for mounting interior cabinets) but I wouldn't use that degraded hardener in anything important.  

The resin was equally old and abused and a traveling partner of the 205, but it hadn't changed color and it kicked just fine when used with 207 (special slow / UV resistant) and a new can of 205 hardener that I used when the old one was empty.  Maybe the hardeners are more sensitive than the resin?

The test idea is really good.  I wouldn't trust either the resin or hardener in a critical application or anything that would be a PITA to clean up if it's discolored or has been stored for any length of time in less-than-ideal temps.  With close to a decade of racing sailing under my belt now I'm only starting to realize how many critical applications there can be on a boat, particularly given the high loads on a mid-sized or larger keelboat with a large sail area.   There are many things that can hurt or kill a crew if they give way under load.  So I'm getting stricter about what I use for repairs.  

 

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