epoxy- opened shelf life

[Steve Tiedman]

I just bought some new JB Weld clear epoxy. Their website says a shelf life of 3 years for all of their epoxies. It says nothing about it being factory sealed nor opened. JB Weld of New Zealand says 25 years! Huh?

If I keep the bottles sealed, in a climate controlled shop, out of direct sun, etc, will this kit last, opened, longer than 3 years? In reality, this two 4oz bottle kit will probably last me 3-5 years, but it is far more economical than squeeze tubes or syringes.

Thanks.

 

[Lou Jacobs]

I have some West System epoxy from my boatbuilding days. Probably 20 years old. The hardener has yellowed a bit, but it works fine. They say if the uncatalyzed resin starts to get thicker, it can be warmed in warm water bath.

 

[JeffSmith]

I have some West System epoxy from my boatbuilding days. Probably 20 years old. The hardener has yellowed a bit, but it works fine. They say if the uncatalyzed resin starts to get thicker, it can be warmed in warm water bath.

Me too. That stuff seems to last forever. Had to warm it up before using it last time - resin had thickened up a bit after sitting around in the shop for a couple of decades…

 

[Dean Center]

I'm with Jeff.

 

[John K Jordan]

Had to warm it up before using it last time - resin had thickened up a bit after sitting around in the shop for a couple of decades…

Same here - had turned in to thick gel. I called West support, said the same thing - put the plastic bottle into bowl of hot water until it's usable. Doesn't affect the strength.

JKJ

 

[Steve Tiedman]

Okay, good. Now, West is probably recognized as a/the premier epoxy manufacturer, but it's not on the shelf of the local hardware store. And I'd have to think JB Weld is is good stuff, too. I know nothing about epoxy chemisty, if, for the most part, most consumer and general light industrial grade epoxies may be pretty much the same recipies(?). I'll just go with what I bought, and if it goes to crap in the bottle after 3 years, it will have been an $18 lesson learned. Thanks.

 

[JeffSmith]

West System is a great company to deal with. Their products are top of the line, but, equally important, they provide the most (and arguably the best) information on how to use epoxies for best results in many woodworking applications. You can spend hours or months going through what they offer free on the web.

 

[Steve Tiedman]

Thanks Jeff, I'll peruse their info offerings.

 

[Neil S]

+1 for West System epoxy

I buy the epoxy in 1Ltr bottles (105) and the fast hardener (205) in 200ml bottles. I decant from those into 100ml syringes with mil markings on them from which I do the dispensing in 5:1 ratio. I take care to avoid cross contamination between my stock bottles, as that can start the epoxy setting, but am less fussy about the 100ml syringes. I have had some epoxy and harder bottles for a decade, but occasionally discard syringes that have become messy.

 

[Gregory Hickman]

+1 for West System epoxy

I buy the epoxy in 1Ltr bottles (105) and the fast hardener (205) in 200ml bottles. I decant from those into 100ml syringes with mil markings on them from which I do the dispensing in 5:1 ratio. I take care to avoid cross contamination between my stock bottles, as that can start the epoxy setting, but am less fussy about the 100ml syringes. I have had some epoxy and harder bottles for a decade, but occasionally discard syringes that have become messy.

Have you considered smaller syringes for the hardener (20ml)?

Gregory

 

[Neil S]

Have you considered smaller syringes for the hardener (20ml)?

Gregory

No, for two reasons, Gregory. It is easier to pour into 100ml syringes and I rarely dispense precisely 100ml of epoxy for which 20ml of hardener would be required. Most of my mixes are much smaller and odd amounts.

Before I do a mix I note how much epoxy is currently in the epoxy syringe then squeeze out how much I think is need onto the mixing card for the job in hand and then note how many ml that was from that syringe then calculate and add 1/5th that amount of hardener. On very small jobs I will often just visually add 1/5th of hardener without measuring it.

 

[Lou Jacobs]

Note that West System, and most other epoxies, the ratio of hardener to resin is by weight rather than volume. Easy to achieve with a small scale measuring in grams. It’ll usually work by volume, but you’re just getting an approximation that way. Also, it’s important to check if the epoxy has UV filters. Most laminating epoxies don’t, so if your item might get much sun exposure, it will eventually degrade over time unless you cover it with a varnish or other UV filters.
Edited to add: I forgot to mention amine “blush”. Unless a laminating epoxy is specifically “blush free” you may wind up with a surface waxy coating over the finished object. It’s easy to remove, but needs to be taken care of before any final finish is added. https://www.westsystem.com.au/wp-content/uploads/2019/07/amine_blush.pdf

 

[Kevin Jenness]

Note that West System, and most other epoxies, the ratio of hardener to resin is by weight rather than volume. Easy to achieve with a small scale measuring in grams. It’ll usually work by volume, but you’re just getting an approximation that way. Also, it’s important to check if the epoxy has UV filters. Most laminating epoxies don’t, so if your item might get much sun exposure, it will eventually degrade over time unless you cover it with a varnish or other UV filters.
Edited to add: I forgot to mention amine “blush”. Unless a laminating epoxy is specifically “blush free” you may wind up with a surface waxy coating over the finished object. It’s easy to remove, but needs to be taken care of before any final finish is added. https://www.westsystem.com.au/wp-content/uploads/2019/07/amine_blush.pdf

Ratios according to volume or weight may differ for a given product but they are as accurate as your measuring methods. It's usually pretty easy to find the weight ratios on vendors' websites but the container instructions almost always use volume. If Gougeon Bros thought it necessary to use weight ratios they wouldn't sell pumps. Using graduated syringes or mixing pots is fine for medium to large mixes. I like to use a gram balance scale for small quantities or thick products that are hard to measure by volume.

Good points about UV protection and amine blush. Unwashed blush can interfere with intercoat adhesion as well as final finishes.

 

[John K Jordan]

the ratio of hardener to resin is by weight ... Easy to achieve with a small scale measuring in grams.

If looking a small inexpensive scale, I've been using several of these for over 10 years for shop and farm tasks. The scale bought back then is slightly different (and was only $8 in 2013!) but functionally the same. I do have a laboratory triple beam balance but these little scales are so much quicker to use. The accuracy checks out.

Amazon.com

For small amounts of epoxy I deposit and mix on a short strip of paper-backed aluminum HVAC tape. Of course, with small amounts you can also just squeeze out two approx equal lines but weighing might give a better bond if that is important. (Can use a small disposable plastic mixing cup instead but usually reach for the aluminum tape.)

JKJ