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I have bought some epoxy glue that I was using for my miniatures.

I have been having some problems with it however - even after leaving it for a few days the glue is still rather soft, with a consistency a bit like hardened bubble gum (i.e., with a bit of effort I can pick it off with my fingernail). It is also not holding very well (i.e., it is rather flexible – again a bit like a gum).

I was wondering whether this could be due:
- to my having to leave it longer to set further (I have left it for 3 days so far)
- the weather being a bit too cold (it has been about 18 degrees Celsius (64 degrees Fahrenheit) or lower for most of the day) – I had heard that some epoxies can require a certain temperature to fully set.
- the recent wet weather making it take longer to dry
- the glue being defective

Does anyone have any suggestions or thoughts?

Most likely culprit is a bad mix. What type of glue are you using exactly?

Epoxies tend to give off their own heat (which accelerates their curing) during their curing time, but low temperatures DO slow down the curing process - once mixed, you cannot stop the inexorable march of chemistry. They will all cure eventually.

The Faster the cure of the epoxy, the more heat that is given off (5 min epoxies get "hotter" than 24 hour cure ones) over a given period.

The 5min stuff still requires a 24 hour cure period to achieve full strength. It sets in 5 mins, but doesn't harden fully until the 24 hour period is up.

The 24 hour stuff generally requires 72 hours to achieve full bond strength.

The glue was supposedly one that should cure within 16 hours (but it noted on the packet that it could take longer in the cold). http://www.ec21.com/product-details/strong-Bond-AB-Epoxy-Glue--5728490.html

Curiously it is also supposed to be a 5 minute epoxy but was still very moveable after 30 mins.

Can you speed up the curing by adding heat (e.g., hairdryer) or is it best to just wait it out? How do you know when it has fully cured (as opposed to it being a case of it never curing)?

The biggest culprit with epoxy not curing is not getting the ratios right and not mixing it properly.

Are you absolutely sure you're mixing it properly and have you been careful about getting close to the correct proportions?

Most epoxy adhesives it's really hard to tell if they're properly mixed, so I just be vigilant and mix for a specific amount of time. If it's a 5 minute epoxy, I usually spend 1 to 2 minutes mixing it, even if I think it's mixed, I just keep mixing it just in case.

Most times my epoxy hasn't cured properly it's been because I was lazy and didn't do that, and a couple of friends who commented their epoxy glues weren't curing I told to do that and it fixed their problem.

Cold weather can most definitely slow curing time to a crawl, but 18 degrees is not cold, you'd be more talking in the sub 10 degrees range before I'd be too concerned.

Just to feedback, AllSeeingSkink's advise was right on the money.

I remixed the epoxy, stirred it for a long period of time (2 minutes) and it has set perfectly (now being hard as nails).