Epoxy taking long time to set

[Alan Lightstone]

I'm running into something odd. I have a batch of West System 105 Epoxy that I've been using a lot lately, that is taking a very long time to initially set (like when using the 205 fast hardener) it still hasn't set overnight.

It takes applying a heat gun to make it set.

Has the hardener gone bad, or the epoxy resin, or am I imagining things?

Temperature is around 72 in the shop, I even turned on the shop heater to heat ambient air temp up to 82, which didn't really help.

[Kevin Jenness]

It is possible you have a bad batch Have you talked to the manufacturer?

Have you had normal results with this batch of resin and hardener in the past and only recently are having problems? If so, I would suspect your mixing ratio (5/1) is off. If you are using pumps check what they are putting out with graduated cups. Make sure the proportions are correct, and that you are mixing the components completely.

I have used West System 105/205 for many years with predictable results, even with old resin that has crystallized and been rejuvenated and hardener that is dark red and smells like ammonia.

[Alan Lightstone]

Yes, the batch has been fine until recently. I am using the pumps. Is the 5:1 ratio by volume or by weight? Would adding additional hardener to see if it sets quicker prove anything?

[Alan Lightstone]

Actually, I just looked it up. It's 5:1 ratio by volume, or 5.19:1 by weight.

[Kevin Jenness]

Additional hardener will not help. You need the correct # of resin and hardener molecules to bind with each other. If the proportions are off spec the result will be also.

[mreza Salav]

You pump might be the problem (I once had this issue and realized it when I saw the amount of hardener/resin left was not proportional).
As far as I know they don't have a shelf life.

[Wade Lippman]

As far as I know they don't have a shelf life.

I have some that is about 15 years old. It is dark brown now, but still works fine.

[Chris Hachet]

Cold temps will affect epoxy also. I was doing some lamination work and my epoxy was setting slowly, moving the lamination work to the kitchen table helped my lamination work but not my marriage.

[Larry Edgerton]

Sometimes if the pump gets a little dirty the spring will not push it all the way to the top of the stroke. I check to see if I can pull it up further by hand. Have not had it happen on the resin pump.

[Chip Seltzer]

Is it possible that your mix has been contaminated by something? Just for example, a very small amount of white vinegar introduced to the mixture will prevent it from setting. Maybe something you are using to clean the joint prior to your set up? I would try one shot of resin and one shot of hardner in a clean cup, mix well and let it sit. It should "kick" within 15 minutes and should get very hot and set quickly thereafter. If it doesn't, I am guessing that either the resin or the hardner is contaminated. Obviously the next step is to replace one at a time until you find the culprit. One mistake can be applying the mix to the wood before the chemical reaction has had time to complete. That requires the mixture to be in "bulk" and not spread out thin. I keep a gallon of West 105 on tap at all times with a gallon in reserve. I keep a quart of fast and a quart of slow as well, pumps always in place. I have never had a properly mixed, clean batch fail to kick.

[Frederick Skelly]

I'd call the manufacturer tomorrow, Alan.

[Larry Edgerton]

Is it possible that your mix has been contaminated by something? Just for example, a very small amount of white vinegar introduced to the mixture will prevent it from setting. Maybe something you are using to clean the joint prior to your set up? I would try one shot of resin and one shot of hardner in a clean cup, mix well and let it sit. It should "kick" within 15 minutes and should get very hot and set quickly thereafter. If it doesn't, I am guessing that either the resin or the hardner is contaminated. Obviously the next step is to replace one at a time until you find the culprit. One mistake can be applying the mix to the wood before the chemical reaction has had time to complete. That requires the mixture to be in "bulk" and not spread out thin. I keep a gallon of West 105 on tap at all times with a gallon in reserve. I keep a quart of fast and a quart of slow as well, pumps always in place. I have never had a properly mixed, clean batch fail to kick.

That is simply not true. The exothermic reaction will complete as long as it is mixed well and your temps are within spec. Your supposition is a disaster waiting to happen on a complicated glueup. In Wests own manual it tells you to spread out on a sheet after mixing to increase the time you have to complete the glueup. They also advise packing the cup in ice if even more tine is needed.

You can speed the process by doing as you suggest, but it is not necessary and compromises the strength of the end product.

[Andrew J. Coholic]

Been using West systems since the late 80's. We use it regularly in the shop for several glue ups where regular woodworking glue doesnt work.

I have never, ever had a problem - and I doubt a bad batch would get through.

I have had the same issues at time with the pumps not wanting to return to the top of the stroke, and I always pull up on them to make sure the next pump gives a full metered amount.

Cold - well, I drop the temps in the winter in the shop to 58 F, and I use a lot more slow hardener than fast. Never had it not harden although the working time is definitely longer. Often I use fast and slow together as well, as long as the # of pumps is the same as the resin your good.

We generally go through the stuff faster than I wish we did (due to the cost) but I have been given some older resin that was discoloured and hardener that was very amber and stunk like ammonia. It still worked fine as the others have stated.

Im a firm believed that if the epoxy fails to cure, user error is probably the culprit... and what I'd investigate first. If you test the batch and it doesnt cure, I'd call them up and send back for testing.

[Alan Schwabacher]

I would suspect the pumps. If one partially clogs and makes the ratio wrong, that will prevent proper cure. For epoxy, as mentioned above, don't change the ratio. Think of the resin as having mortises and the hardener tenons: only the correct ratio will make the structure you want. If you change the ratio, you may make something, but it won't be the same structure.

Another possibility is crystallization. If you store the epoxy for a long time in cool temperatures, you might see solid on the bottom. This is crystallization of the epoxy. Mixing it with hardener will make it behave as if you had the wrong ratio because the solid part does not properly mix in.

You can bring crystallized epoxy back to proper behavior by warming and stirring until it dissolves. Then on mixing with hardener it will harden as usual.

[Chip Seltzer]

That is simply not true. The exothermic reaction will complete as long as it is mixed well and your temps are within spec. Your supposition is a disaster waiting to happen on a complicated glueup. In Wests own manual it tells you to spread out on a sheet after mixing to increase the time you have to complete the glueup. They also advise packing the cup in ice if even more tine is needed.

You can speed the process by doing as you suggest, but it is not necessary and compromises the strength of the end product.

My point is simply that spreading the mix before the reaction is underway can result in incomplete set. I have done a lot of this and have used ice to extend pot life on many occasions. In this case, the post is about a mixture that did not harden and that is a possible reason. My suggested "test" was to see if the problem exists in one of the cans (resin or hardner) or if it has something to do with his application.