G-Flex epoxy not curing hard

E

EGA

Joined
Apr 12, 2018
Messages
19
On the recommendation of several posts on this board, I purchased West Marine's G-Flex 960 epoxy. It has a 'gel time' of 3-4 hours and an inital cure time of 7 hrs.

After 7 hours, it does not seem to be cured yet. I can make a mark with my thumbnail in a hardened pool of it. I am writing to check whether the 'flex' in the name implies that it will not harden the kind of rock-hardness i am famliar with in other (5 minute) epoxies, or if I really have messed something up (presumably not measuring out accurately). I measure by eye, not weight, though I thought I had gotten the 1:1 ration pretty accurately.
 
I use G/flex but I don't believe it's the same stuff you're using. My bottles are labeled 650-32A (resin) and 650-32B (hardener). At 7 hrs in, yes I can still dent the mix with my nail. It cures to a solid in 3-4 hrs but isn't fully cured for 24 hrs at 72 degrees. I try to wait 48 hrs before messing with it just to be safe.
 
It doesn't get to "brittle hard" like 5 minute epoxy, but it definitely gets so hard that you aren't going to press your nail into it. Give it warmth and time like Adam says.
I had these little plastic epoxy applicators I used to use. Would let epoxy dry on them, flex them a bit and it would crack and peel of easy. Started using G Flex and bending them doesn't "crack" the epoxy and let me peel it off. It sort of flexs and is super strong. I wound up cutting the stuff off until I wrecked all my aplicators and went over to using popsicle sticks that I just toss out.
 
I've never seen 960, but I weigh out 650 because I used to run into problems before I bought a little scale to measure the mix.
 
What was your method of mixing your Gflex?
 
Thanks all for you advice . I was wrong about the epoxy type, it is standard g-flex 650. I mixed it with the back of a plastic fork vigorously and thoroughly. It seems to be setting up a bit more now, so I’ll leave it and see
 
These high grade resins need exact measuring. The bottles have the ratio by volume and by weight. Most makers use the weight method and a good gram scale. Mixing by volume is a bit tricky in less than 1 oz. to 1 oz. batches.

The ratio is 1:1 by volume, and 1.2:1 ( resin to hardener) by weight. That is 6 grams resin for every 5 grams of hardener.

The gel time is 3-4 hours, set time 6-7 hours, and cure time 24 hours. It will continue to harden for a couple more days.
 
I don't work on a knife for at least 24 hours after epoxy application of the handles. I also like to keep the little cup and stirring stick, that way I can test how well cured it is and whether I got the mixture right. If it's not yet hard and cured well in the mixing cup, it's not going to be on your knife either.
 
I use the 650 and as stated you want to get as 50/50 as possible. Then wait 24 hours and if it’s below 65 degrees I wait 48 just to be sure., this stuff is far Superior to any of that 5 min stuff that I won’t ever use again!
 
Stacy E. Apelt - Bladesmith said:
These high grade resins need exact measuring. The bottles have the ratio by volume and by weight. Most makers use the weight method and a good gram scale. Mixing by volume is a bit tricky in less than 1 oz. to 1 oz. batches.

The ratio is 1:1 by volume, and 1.2:1 ( resin to hardener) by weight. That is 6 grams resin for every 5 grams of hardener.

The gel time is 3-4 hours, set time 6-7 hours, and cure time 24 hours. It will continue to harden for a couple more days.
Click to expand...
Exact measure....how dicey is it? I have only used up about 20 oz of gflex. I have little graduated medicine cups, Squeeze in the same amount of resin and hardener by eye. Done it in all sorts of temperatures and humidity conditions(even outside under a tent in the rain twice. I haven't worried that much about being SUPER EXACT and it has always hardened and been fine. Am I just lucky?
 
I use either 1 cc or 3 cc syringes to draw up my G-flex. thats my measure method. Of course never put the hardener syringe into the resin bottle or vice versa. I also actually set a timer and mix for 4 minutes using my little stir stick in a small plastic mix cup. Throw away the stick, the syringes, and the mix cup after each batch. Warm temp for 24 hours. Never a failure. Great stuff and you can add color with no problem. I usually put in a speck of black.
 
I too use bulk syringes without needles. Cheap from the vet supply store. Pennies each. If you really wanted to you could reuse them since you use one for hardener and one for resin, just store them in a disposable cup or something.

Also, if something isn't curing enough to work with fast enough for me I often put it in the dehydrator at 100F. Going from 70F to 100F isn't enough to weaken the bond IMO but it definitely is enough to speed up the cure time.
 
Mix ratio is very picky. I used to use graduated medicine cups, and had a few batches fail to cure as that evidently wasn't close enough.
I since switched to a loctite epoxy with their dispenser gun, and have never had another epoxy related issue. I always keep the mix cup until it cures so I can insure nothing went wrong that I wouldn't notice on minimal squeezeout. I find the loctite to be better epoxy, and its less fuss, for me its worth the extra money. I use about a case a year of the tubes.
 
Stacy E. Apelt - Bladesmith said:
These high grade resins need exact measuring. The bottles have the ratio by volume and by weight. Most makers use the weight method and a good gram scale. Mixing by volume is a bit tricky in less than 1 oz. to 1 oz. batches.

The ratio is 1:1 by volume, and 1.2:1 ( resin to hardener) by weight. That is 6 grams resin for every 5 grams of hardener.
Click to expand...
Going forward I think I’ll just measure them out by weight and be done with being worried about it. Thanks.
 
EGA said:
On the recommendation of several posts on this board, I purchased West Marine's G-Flex 960 epoxy. It has a 'gel time' of 3-4 hours and an inital cure time of 7 hrs.

After 7 hours, it does not seem to be cured yet. I can make a mark with my thumbnail in a hardened pool of it. I am writing to check whether the 'flex' in the name implies that it will not harden the kind of rock-hardness i am familiar with in other (5 minute) epoxies, or if I really have messed something up (presumably not measuring out accurately). I measure by eye, not weight, though I thought I had gotten the 1:1 ration pretty accurately.
Click to expand...

Don't do that.


Mix ratio
Clean surface prep
temperature
through mixing
Fresh product.

All matter

Get a cheap gram scale, use a disposable tray, tare it out, use the ratios given for weight not volume.
 
You must log in or register to reply here.
Back
Top