Mixing small batches of epoxy

[Alan Gage]

It's hard to do accurately. I used to mix my epoxy using a small, analog, kitchen scale. But I'd always run out of resin before hardener so I figured I better come up with something more accurate.

I've got pumps for some of my epoxy but even the minimum number of full pumps is way too much epoxy for many jobs and I hate to waste it. Eyeballing partial pump squirts can work but that gets dicey. This is what I've been doing the last last few boats and it's worked well so far. Today I wanted to mix up about 1 1/2 ounces, which is roughly 45ml. My epoxy is a 2:1 ratio so that's 3 parts total. To get 45ml that means I need 15ml of hardener and 30ml of resin.

I start with a very small measuring cup and pour in 15ml of water.


20141218_001 by Alan Gage, on Flickr

That water gets dumped into my mixing cup, onto which I've put a piece of tape. Put a mark on the tape at the 15ml waterline. White tape works better but it appears I'm out.


20141218_002 by Alan Gage, on Flickr

Pour that water back into the measuring cup and then fill the measuring cup to 45ml. Now dump all the water back into the cup and mark a second line on the tape:


20141218_003 by Alan Gage, on Flickr

Now throw out the water and dry the inside of the cup. Fill to the first line with hardener and then top it off to the second line with resin.

45ml is about as small as I can go while still maintaining enough accuracy for it to setup properly each time. It only takes a small error in volume to throw the mix off considerably with these low doses. The larger the batches the more accurate it is.

Reason for the small batch today was that it was thickened and tinted to fill any gaps before fiberglassing the stripper I'm working on.

Anyone got a different/better way?

Alan

 

[stripperguy]

Alan,

I have two syringes that I keep in graduated 1 quart polyethylene paint mix buckets. One bucket and syringe for the hardener, one for the resin. Each syringes holds 60 mL, or about 2 oz.
When I'm in need of small batches of resin, I pour some resin and hardener into the buckets, draw the stuff into the syringes, and then squirt into whatever mixing container is hanging around.
That way, I can accurately mix very small batches, without goofing up the ration (also 2:1). Batches as small as 45 mL are no brainers, even a 15 mL batch is do-able.
When I'm done for the day, or a few days, I just pour what's left back into their respective gallon jugs.

I also have the one shot pumps, but I agree, a 3 oz minimum batch is wasteful when you only need a few dibbles. (is that even a word? dibble?) Make that dribbles.

And you didn't ask, but for larger batches, 12 or 16 oz at a time, I measure and mix directly in the same graduated paint mix buckets. I use a fresh bucket for each batch and leave the stir stick (a clean cut strip) in each used bucket. Later, like a day or so, I flex the bucket and use the left behind stir stick to cleanly pull out the thin layer of left behind resin. I have probably about 6 or 8 of these graduated buckets in the rotation when I'm glassing, some clean, some waiting to kick.

 

[Alan Gage]

I like the syringe idea, I'll have to get some from my vet if I can remember.

I use the larger graduated containers for mixing large batches as well. I like the idea of leaving the stir stick in the resin in order to pull out the whole wad later. I've been rolling large batches lately so they go straight from the mixing cup to small paint tray. When I'm done mixing I clean the mixing container out with denatured alcohol. I find that easier than trying to get out all the little flakes if I let the skim coat harden.

Alan

 

[Glenn MacGrady]

The only epoxies I've used are five minute epoxy and G/Flex.

The five minute epoxies typically are mixed 1:1 and come in a dual syringe. Just squeeze out any size dibble you want and it's in the right proportion.

G/Flex is a "real" epoxy that is also mixed 1:1. It's easy to squeeze out approximately same-sized microdibbles of resin and hardener without any measuring device. Then stir with a sterling silver toothpick and apply with tarantula hair eye lash brush.

 

[Guest]

We use tiny plastic cups for communion at my church. I collect the used ones and wash them out. they are perfect for small batches of resin and liquid epoxy, small batches of anything ect. I just throw them away after. recycled and free. I will do the same with our candlelight Christmas candles. I give them away for fire kits and to the scouts.
Merry Christmas,Turtle

 

[Holmes375]

If I'm just doing a few quick small batches I use the syringe method. Very accurate and easy. If I'm making parts or other tasks where I'm going to need a number of small batches I get out the lab scale and measure by weight in grams. With my epoxy and resin in ketchup-style squeeze bottles I can quickly and accurately make small mixes to use as glue, edge sealing, etc.

 

[Alan Gage]

Stopped by the vet's office when I got off work and picked up some nice 30ml and 60ml syringes. That will be a lot nicer than the way I was doing it.

When I first started working with epoxy it seemed like a no brainer that weighing would be more accurate that trying to measure by volume and maybe if I'd had a more accurate scale that would have been the case. But every time I'd see instructions from an epoxy manufacturer they always specified measurement by volume. Then I heard a couple people say the resin and hardener aren't always the same weight and that was the reason for volume measurements rather than weight. I have no idea of this is true or not but I can see where an accurate scale with hardener and resin in a squeeze bottle would be very handy for mixing multiple small batches efficiently.

Alan

 

[Holmes375]

Yes, an accurate scale is vital. Mine is an older digital lab scale that is very accurate and consistent. Econo scales are often not accurate enough or just not consistent in terms of small weight measurements.

Resin and hardeners are indeed often different in terms of weight & volume. I get the ratio by weight from the manufacturer and then make up a quick reference chart to make specific volume batches. With multiple resins on hand I just have to make sure I use the right chart for the resin in play. Don't ask how I know that....

 

[Guest]

I have developed a good eye for estimating for the amount of small batch epoxy I need to mix and I’m always pleased when I come out with just the right amount. Even my G\flex bottles, usually mixed by eyeball estimation, come out even in the end.

None the less I try to have another less-critical epoxy job prepped in the wings awaiting any excess, some home/garden/tool or other repair. Even if it is just smearing the last out of the brush that use of every little bit pleases the Scotsman in me.

It is one more thing to remember to do, and one more prep job, but a lot of those secondary epoxy dregs jobs are things I probably wouldn’t mix epoxy for as a primary task.

 

[smallworks]

. Then I heard a couple people say the resin and hardener aren't always the same weight and that was the reason for volume measurements rather than weight.
Alan[/QUOTE]

I've been wondering about this, too. I use epoxy resins for other projects (art) and it's always a crap shoot shoot, no matter how carefully I'm measuring with pumps. I use West System epoxies - 1:1 ratio.

 

[Canotrouge]

that is how I've been doing it fo years, sort of, I use a plastic drinking cup, and I mark right on the cup with a sharpie... I hate to waist epoxy too!!

 

[sloride]

I've never used epoxy,This is interesting and informative

It will come in handy if I decide to epoxy in footbraces or bar

 

[ppine]

I like the metered pumps for regular amounts of mixing. Your method probably works fine for small amounts. I used to do lots of water quality sampling in the field involving techniques like titration. I learned that to be accurate with small quantities of liquids, you need small graduated containers. So for small amounts of measured epoxy, I use a small graduated mixing cup. It looks like a large shot glass and is very accurate. A Sharpie is used to highlight the most popular marks.

 

[Guest]

. I use West System epoxies - 1:1 ratio.

I know West G/flex is a 1:1 mixing ratio, but I believe others are 1:5 or 1:3.

 

[smallworks]

I need to clarify my former post- the West System Epoxy ratio is 1:1 if using the pumps provided. The actual ratio is 3:1 . Mike, are you using pumps or free-pouring with the G/flex bottles? Are you satisfied with this product? Thanks...