Laurence-RCU

I aim to use equal parts of the two epoxy tubes but of late the end product stays somewhat tacky, even after many days of curing. I have not have this problem in the past.
What is the shelf life of epoxy?
What am I doing wrong?

Laurence

Hydro Junkie

It could be several things:
1) beyond shelf life, depending on the brand that you didn't give
2) conditions in which the epoxy was used(i.e. temp, humidity, etc)
3) thinning(some don't take too thinning well)
4) contamination by other stuff/chemicals
5) using a different brand hardener than resin
6) incompletely mixed, preventing total cure
These come from the top of my head, could be more

flyinwalenda

My Feedback: (5)

You were either way off on the equal amounts or it has spoiled.
Superglue acts the same when it spoils .

jetmech05

I'd say it's old

Laurence-RCU

Thanks for the replies. I believe age was the problem.

Now I have another question.

I have been able to pull apart the joint and now have these surfaces with the "tacky" epoxy exposed. I am supposing I should not apply fresh epoxy over these surfaces, but how do I remove the old epoxy?


Laurence

FLAPHappy

My Feedback: (209)

I used to use old plastic from wrapping on different parts I purchased, saved all that plastic to mix epoxy. Well, I had the same problem, so I switched to plain paper plates, no more problems. Must be a chemical in that plastic that would not let the epoxy set when mixed Just my expierence..

Rodney

Mixing epoxy in a container containing a wax coat or lining can cause the epoxy to not cure well. Also, thinning with alcohol can cause this problem, especially if the alcohol contained a lot of water (which all medical alcohol does). It is best to NEVER thin epoxy, use heat to make it flow well. If you must use alcohol, use denatured and prepare to put up with a weaker bond.

raptureboy

West systems recommends using a solvent like acetone or lacquer thinner and very sparingly rather than alcohol because of the water getting trapped in the epoxy making for a weaker epoxy. Heating is the most preferred way. I agree, most likely it was old and if you use the heat gun it will soften up and can be scraped off.

speedracerntrixie

My Feedback: (29)

I have never had epoxy go bad and that includes a couple gallons of laminating epoxy that I got from work 4 years ago. I still use it from time to time. I however keep it sealed well and out of light. 99% of the time it was mixed improperly. Either wrong ratio or not mixed enough. Second thing I would consider is temp. Most ambient cure expoxies cure best above 70 degrees. If your shop was below 60 degrees it will affect the cure. Lastly I feel that most 1:1 ratio hobby epoxies are junk. IMO it's best to pick up a quart kit of a good quality laminating resin, some milled fiber and some Cabosil to use for pretty much all occasions. Using it strait it's great for applying fiberglass cloth or just fuel proofing engine compartments. Add some Cabosil to form a paste and it's a great epoxy glue that won't run or drip. Add some milled fiber to the paste for additional strength. A 45.00 investment will last years.

Hydro Junkie

I love it, everyone agreed with at least one of my possible causes. Guess I get lucky occassionally

DavidAgar

My Feedback: (108)

I use Bob Smith epoxy and it never goes bad. I do thin it on occasion with Isopropyl Alcohol which is 99 percent alcohol and I have never had any issue's with it not setting up. Good Luck, Dave

Tom Nied

I've never had epoxy go bad because of age. We don't know which epoxy he was using. I have had bad epoxy curing when I accidentally grabbed the wrong hardener. Now I keep all epoxy bottles rubber banded together so that I always grab the two matching bottles (resin & hardener). Mixing. Go to a craft store and buy a box of 1000 Popsicle sticks, it'll last a long time. 5 minute I'll mix for 3 minutes, 10 minute I'll mix for 5 minutes, 30 minute I'll mix for 6 minutes. A watch with a stopwatch helps. If I'm in a gluing process, I won't answer a phone because of the priority of the process.

dirtybird

My Feedback: (5)

Have you tried mixing in one of those little blue pills?

FBaity

My Feedback: (2)

How old is too old?

loopdeeloop

My Feedback: (4)

I save soda bottle caps and some larger plastic container caps for mixing small amounts of epoxy and fiberglass resin. I mix the epoxy with a round toothpick. I cut the sharp end off to create either a blunt or tapered end and use it to daub the mix onto the parts to be joined. Toss the cap when finished. Use of bottle caps also helps prevent mixing too much material which you end up wasting.

do335a

I've never had any brand of epoxy go bad because of age, regardless of brand. Had some for over 20 years.

What is critical is the mix proportions. That's easy to get wrong, even by a small amount, especially when mixing a small batch. If you have too much hardener, the mix stays rubbery, will not set for a long, long time. Never gets hard. Also, that mix will not have maximum strength.

To get better accuracy with my mixes, I use a set of baker's measuring spoons and mix in a clean styrofoam cup. NEVER, NEVER do I just squeeze a bit out of the container and guess that the amounts are equal, 2:1 or whatever proportion is called for. No problems. Clean up with the alcohol on a paper towel and then pitch it.

It's also important to be certain that the resin and hardener are completely and thoroughly mixed. Fold in the stuff on the sides of your mixing container as you go to ensure that it all gets thoroughly mixed.

If you use alcohol to thin it, get the 99% stuff. The 70% variety has too much water. Use the alcohol sparingly. Too much ruins the glue. Mix resin & hardener first. Then add alcohol and mix again.

To clean up the bad stuff on your build, use the alcohol and paper towel. Make certain that you clean off the excess alcohol completely before reassembly. If it's too far set for that and still rubbery, peel, cut, rub or scrape it off. Just be certain to get rid of it all..

If your epoxy components crystalize in their containers, simply warm up in the microwave oven and presto - liquid and totally usable again.

Laurence-RCU

Many thanks for the replies. It has answered my questions. I need to be more accurate with the mixing.
Concerning the removal of the old "tacky" epoxy; it was suggested; use a heat gun, scrape and then acetone.

Laurence

John_M_

Hee hee , I don't think viagra would help much.




I use the loctite brand epoxy... I've had some that was so old the part A resin started to crystallize in the bottle... I just put the bottle in some hot water, 130 degrees and let sit there until the bottle and resin got heated through... the resin reconstituted back to normal and still works just fine.



John M,

Billy J

My Feedback: (4)

if using west you need the squirt dispencers that measures it perfectly every time ! if not mixed for at least 3 minutes using 206 hardener you will have trouble . Good luck

Tom Nied

These are pretty good for measuring out epoxy. Graduated Medicine Cups 1 oz http://www.ebay.com/itm/Medline-Plas...item3cf0f5e6f8 Sometimes I can get more than one use by letting the unused epoxy cure then pulling it out later. Also, if you have an accurate 4 beam gram scale, you can measure out epoxy by weight. I've done this, it's a bit tedious, but will give you accurate measurements. Again, mixing well is important. Also beware, the more you mix as a batch, I've noticed setups quicker and produces heat. Epoxy is probably the heaviest glue we use, so drips are adding weight we don't need. It doesn't evaporate as it sets, so what you use will add weight to your model.

Probably more than you wanted to know about mixing epoxy. Epoxy is a great adhesive, use it wisely.

rcmichael

My Feedback: (21)

I wood say you have a boner of a problem!

049flyer

My Feedback: (18)

A wire brush on a dremel will remove epoxy with minimal damge to the underlying wood as long as you are careful. I have tried other brushes on the dremel with good results but slower epoxy removal.

rt3232

My Feedback: (6)

To the op
All of the above post are good and most likely come from experience, So I would say temp & humidity, egual/parts and mixing are your most likely problems. That said what to do, use some heat from your heat gun, say 30 min intervals will force cure, If that does not work heat and dig it out and clean with acetone, and start over.
I would add do NOT use any type of paper cups, some medical plastic cups will get soft do to the cem's in the epoxy (the best thing I have found are the little 2 oz. fruit cups) then if you have a Harbor fright store in your area pick up a small weight scale grams/oz for about 10 $ and mix all epoxies by weight
any ratio. Doing it this way I have never had a bad mix, But you MUST mix it thoroughly.


Now I will go back to my dish and watch


Cheers Bob T
AMA13377

JPMacG

My Feedback: (2)

Hobby epoxies seem to cure at an exponential rate. After a few hours it is somewhat hard. After a few days it is pretty hard. After a few weeks it is totally hard. Temperature matters a lot.

I have had particles form in the hardner (or resin?) in old epoxy. If I heat the hardner then the particles go back into solution and the epoxy seems to cure normally.

Hydro Junkie

I ALWAYS mix my epoxy in the mixing cups sold at the hobby shops and woodworking stores. By doing so, it eliminates the chance of getting wax or other contaminants into the mix that is possible when using containers that had other products in them. As someone else said, you let the excess cure at least overnight and you can pop it out and reuse the cup. I've used some cups up to a dozen times before discarding. Only time I had West Systems not cure I had glued up some parts and left them in the garage. That night, the temperature got below freezing outside and close to it in the garage. Even using low temp hardener, it was just too cold to cure properly. By using epoxy in a 60F+ room, I've not had an issue since. It is shown, on most packages of good quality epoxy, what temperature range the epoxy can be used with optimal results. This is definitely true with West Systems so I would recommend that you READ THE PACKAGE OR MANUFACTURER'S WEBSITE BEFORE USE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!