Epoxy didn’t set, now what?

So this message is only loosely climbing based but relatable. 

With epoxy glue ins it’s pretty simple to get catalyst and resin to mix evenly and harden well. Most have an applicator that mixes it for you. Has anyone ever experienced a bad mix? Something that didn’t harden properly? How did you remedy this?

  My experience isn’t with the same epoxy, however I mixed some to repair a surfboard. That stuff is very different and very similar. Same concept but it’s a 2:1 mix rate of resin to hardener. The measurements seem much more critical. Most of my repairs came out perfect but I have one area that remained tacky. Now what? 

  I’m hoping someone out here has had a similar issue. Do I add a small amount of hardener and try to mix it? Scrape it off? Use some kind of acetone or paint thinner? Thanks for any help. 

I used to make longboards and I've had epoxy not set before.  It was usually (Edit:only)  in a similar instance you had where I was mixing small batches where I'd just eyeball the amounts. The heat idea can work but if your ratio was off typically it will remain tacky and won't progress past a certain point in the curing process.  I wish I had a good answer for you but when this has happened to me i've scraped off the epoxy and used vinegar or acetone (depending on the how sensitive the material the epoxy is on is.)   

Adding hardener hasn't worked in my experience.  Once it's jacked I haven't found a way to get it to cure properly.

Also I'm not a surfer but in my experience acetone doesn't bother cured epoxy on glass or carbon.  Do a test patch obviously.  It's a mess to clean up and fix i've been there.

Elbow grease it is. Thanks guys. Great advice about the vinegar I’ll try that. 

Adhesives do occasionally have bad tubes. A very experienced rebolter (who'd also used glue-ins for years in the construction industry) working with ASCA support had a bad tube of AC-100+ a few years ago. He found that it was not setting despite an extended time period, then ended up pulling out the bolts, cleaning out the epoxy with drill bit and brush, then placing mechanical bolts in the same hole. We had another couple tubes from the exact same batch and I tested them in similar temperature and humidity and they set fine. So it was a single bad tube.

Glad you brought that up. I’ve drilled many epoxy holes in concrete under the eye of an inspector. I remember one telling me about that