Thread: Epoxy troubles

Don't mix by eye in a plastic cup, you will get it wrong ... eventually.

I use electronic scales and do it by weight (I also use West but it's the same principle) but there are all sorts of methods by volume - quite a few were discussed in the last couple on months on this forum in some thread that I can't remember the name of but it's worth tracking down if you can because there were some creative and good ideas in it.

As for your current mix. Leave it for another day or two to give it a chance.

The standard line is that if you get the mixes a little wrong, they won't work and if you did two next to each other, they should both cure at the same time.

Experience with dodgy pumps tells me that you can get away with bodgy mixes but that you shouldn't rely on it.

Experience also tells me that sometimes the transition from feeling soft to feeling hard is very quick so it might be that your 'soft' mix is still en route for a successful set.

Cynicism suggests that epoxy can be like computers and deliberately stuff you around just to mess with your head

I've had mixes inexplicably take longer to set than I anticipated but have gone on to be successful - temperature and humdity both play a part. If you're moderately careful, it's unusual to have a mix not work however, pulling the clamps too early is unfortunately common so ... just wait until tomorrow before worrying about a 'soft mix'.

Richard

Yeah I had been using the cup in cup method for larger quantities but it seemed a bit OT for the small quantity I was mixing. I will definitely do it next time.

On the plus sid eI just rechecked the pox and it may be hardening up as you said. It is hard to tell at this stage (it is still way to soft) but it does seem a little better than earlier in the day.

Originally Posted by hereselmo1

On the plus sid eI just rechecked the pox and it may be hardening up as you said. It is hard to tell at this stage (it is still way to soft) but it does seem a little better than earlier in the day.

You get caught from time to time - the gunwales that are currently on the boat needed an extra day to set whereas they're normally ready the next day. That was in humid weather too.

Richard

It is rare that epoxy doesn't go off. The two main reasons when it doesn't are that it either has not been measured properly or it has not been mixed thoroughly in the containers.

The most convenient method for measuring (apart from pumps) is to use a parallel sided tin can - petfood/baked bean and use a stirring stick marked with different distances.

The epoxy I commonly use is a 2:1 ratio so I would mark 20mm from the end of the stick and then another mark 10mm further up. Or any such measure.

Best wishes
Michael

Originally Posted by hereselmo1

Yeah I had been using the cup in cup method for larger quantities but it seemed a bit OT for the small quantity I was mixing. I will definitely do it next time.

Small quantity could be a large part of the problem - my view is that the smaller the mix the more accuracy is required because an error of say 1g in 5 is 5 times greater than 1g in 25. There is also more effect from material on the surface of the mixing container that is not mixed as well.

I use a 1:5 epoxy so that exaggerates small measuring variations even more but by using an electronic scale I've never had the wrong ratio. The only bad batch I ever had was from being distracted and forgetting to mix it .

Good point Bob, I was going to write that but kinda got a bit slack! The glue stick marking method works particularly well with 2:1 ratio epoxy or other ratios with bigger volume.

The quantities I am mixing up to glue one chine, a tim can would be way too big.

Originally Posted by hereselmo1

The quantities I am mixing up to glue one chine, a tim can would be way too big.

Mate, get some electronic scales, you can do very small quantities quite safely and easily. One advantage of the scales over the other methods is that if you squirt in too much, it's not hard to work out how much and compensate ... though we're getting into really pedantic boat building here

I've got lazy in my old age and just use the pumps and ignore the waste ... mind you, I use West so a 'basic' mix is roughly 1/3 of a 'basic' Bote Cote mix.

Richard

for those that don't understand the differences between the Bote Cote pumps and the West pumps:

West (5:1) uses one pump of resin and one pump of hardener, the hardener pump giving 1/5th the amount of goop from the resin pump.

Bote Cote (2:1) uses two pumps that deliver the same amount (roughly the same as the West Resin pump) so you have to pump out two lots of resin and one lot of hardener, a system that can lead to a bit of waste in small jobs.

DIGITAL GEM 0.1 X 1000 GRAM DIAMOND POCKET lab SCALE - eBay, Scales, Medicine, Science, Business, Industrial. (end time 14-Feb-10 23:19:44 AEDST)

Under $10 including postage. Accurate to 0.1 gram. I have the identical one and they are great for small batches of glue.

Ok Ok i get it i bought them! lol.

I am noe the proud owner of new digital scales that are currently somewhere in china.

ooooh, geee, I wonder if I can get a percentage of that sale... (actually, looking at the listings there just cost me some $11 for three power supplies)

By the way do I need to allow for the density difference between the epoxy and the hardner or do I just mix it 2:1 by weight?

p.s. the Pox is much harder but I can still dent it with my finger nail. looks like I might have to pull it apart again. I will take some pics when I do.

I got out my epoxy stuff this afternoon ready to do some gluing, i got the bote coat stuff, with the pumps, but the pumps dont screw onto the bottle of resin or hardener...
I used them anyway hahaha
Mike

Originally Posted by hereselmo1

By the way do I need to allow for the density difference between the epoxy and the hardner or do I just mix it 2:1 by weight?

Nah, just mix it 2:1.
Similarly with West (though you use 5:1 there )

Wrap some Glad Wrap around the scales too, or stick them in a bag or something, they WILL get poxy all over them.

p.s. the Pox is much harder but I can still dent it with my finger nail. looks like I might have to pull it apart again. I will take some pics when I do.

Just leave it mate. Give it a few more days ... unless you want to clean it up and do it again.

Richard