5 Minute Epoxy Observation

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Mortalis

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I've been using J-B Weld 5 minute epoxy for quite some time. I mostly use for filling voids and large cracks in the wood turnings. I've noticed that the working time on this epoxy was long enough that I could deep pour a void and then have to wait at least until the next day to do anything with the piece. I also noticed that the epoxy never really hardened up and just wrote it off as this was how 5 minute epoxy was. it would eventually become very solid but always felt like a Urethane Bowling ball. It seemed to serve my purpose and didnt really think much about it. Just seemed it was how it was.

A while ago I was reordering some BSI (Bob Smith Ind.) CA glue from Amazon and I noticed BSI also put out a 5 minute epoxy so I bought a small amount. Well, I am working on a bowl and it has quite a bit of punky areas and one void that once I got the bottom of the inside of the bowl fouund it went all the way through the bottom. I walked by the BSI epoxy I had ordered and said to myself, hey! lets try this stuff out. I used my Gaffers tape and sealed off the void from the outside, mixed up a good sized quantity of the BSI epoxy and added some coffee grounds. I poured the mix into the void and then also poured some into a smaller voind that became apparent but does not go through. By the time I finished the filling the second void I noticed the first one was already set. I read the label on the BSI bottles and it states set in 5 minutes, can be handled in 10 minutes. Full bond strength in 1 hour. I came back after an hour and boy were they right. After the one hour the epoxy was hard as hard plastic. The BSI brand was harder in one hour than the J-B every was after 24 hours.

Has anyone else had this experience with using epoxy? The BSI epoxy almost cures too fast but I guess I dont mind because the outcome is better IMO.

By the way, I just checked and the BSI epoxy was Last purchased Sep 8, 2023, never opened. The J-B is a bit older.
 
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Sounds to me like your mixing of the JB was a bit off - not enough hardener.

I like bsi epoxy, they have 15 and 30 minute open time varieties also. I like the 15 minute for gluing in multiple tubes in multiple blanks - effectively batching out that step.

I can't recall any issues ive had with JB.
I'd check the label to make sure it isn't a "by weight" mix instead of a by volume mix. Maybe the hardener is lighter and needs more volume to fully cure the resin?
 
I have always used the BSI epoxies.

I started with the 5 minute (when making component pens). I find the open time to be somewhat less than the advertised 5 minutes.

When I started making bespoke/kitless, I switched to the BSI 15 minute for the increased open time. In my experience, it begins to thicken up at 7-8 minutes.

I have recently switched to the BSI 30 minute and like it the best. I have tons of open time.

The upside is that the slower the cure, the more flexible and strong the final bond is!!
 
I use Two Ton epoxy with a working time of about 30 minutes. Can do four or five pens at one time. Let it set up overnight and then turn. Got it off Amazon; comes in 4.25 ouncebottles. Used it for building golf clubs.
 
d_bondi said:
I have always used the BSI epoxies.

I started with the 5 minute (when making component pens). I find the open time to be somewhat less than the advertised 5 minutes.

When I started making bespoke/kitless, I switched to the BSI 15 minute for the increased open time. In my experience, it begins to thicken up at 7-8 minutes.

I have recently switched to the BSI 30 minute and like it the best. I have tons of open time.

The upside is that the slower the cure, the more flexible and strong the final bond is!!
Click to expand...
I was thinking of trying the 15 minute. The 5 minute seems to cut the, "what else should I cover with this batch" time really short.
 
Woodchipper said:
I use Two Ton epoxy with a working time of about 30 minutes. Can do four or five pens at one time. Let it set up overnight and then turn. Got it off Amazon; comes in 4.25 ouncebottles. Used it for building golf clubs.
Click to expand...
30 minutes is kinda long for me when I'm filling voids in a curved surface. Just more time for the epoxy to run. Plus my use is decorative mostly, dont need a lot of strength.
 
Jarod888 said:
Sounds to me like your mixing of the JB was a bit off - not enough hardener.

I like bsi epoxy, they have 15 and 30 minute open time varieties also. I like the 15 minute for gluing in multiple tubes in multiple blanks - effectively batching out that step.

I can't recall any issues ive had with JB.
I'd check the label to make sure it isn't a "by weight" mix instead of a by volume mix. Maybe the hardener is lighter and needs more volume to fully cure the resin?
Click to expand...
Hmm, could be. I've always just guesstimated equal parts when I put it on my mixing plate.
 
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