Mixing Epoxy

[James Baldwin]

Hi I need to mix some Epoxy. I'm using System 3. I've mixed it before just by using one squirt for each pump on the bottles and it worked well. This was with the old pumps. With my last order I got new pumps and according to System 3 one full push should give one ounce but they say measure. So when I measure should I be using fluid ounces? I'll be weighing on a very accurate scale. Thanks, Jim

[Jamie Buxton]

Ounce is a weight -- something you could measure with your scale. Fluid ounce is a measure of volume. System 3 should be clear about which they mean.

[Richard Coers]

“DISPENSING USING WEIGHT OR VOLUME MEASURES

To measure 105 Epoxy Resin®, 205 Fast Hardener® or 206 Slow Hardener® by weight, combine five parts resin with one part hardener. Small quantities can be mixed by volume at the same ratio.
To measure 105 Epoxy Resin, 207 Special Clear Hardener™ or 209 Extra Slow Hardener™ by volume, combine three parts resin with one part hardener. By weight this would amount to 3.5 parts resin : 1 part hardener

[Thomas McCurnin]

I've used System 3 for more than a decade and have never noticed much of a difference when varying the resin to hardener ratio. Perhaps it might cure faster with more hardener, I don't know, I've never timed the stuff.

[Jimmy Harris]

If it says ounce, then measure ounces. Some scales have settings for fluid ounces, but as Jamie Buxton said, fluid ounces are technically measurements of volume. An ounce is 1/16th of a pound. A fluid ounce is 1/8th of a cup. If measuring water, one fluid ounce is equal to about 1.0432 ounces. This is the idea behind some digital scales having a setting for fluid ounces. Units can be confusing. Like we think of grams and pounds measuring the same thing, but technically, grams measure mass while pounds measure the force (of gravity). So you'd weigh the same amount in grams on the moon, but your weight in pounds would be much less, if measured correctly. Again, most digital scales with both settings approximate mass based on the idea that your gravity will be the same, or close enough, pretty much anywhere you're likely to measure it on earth.

Having said all of that, with epoxy you're more concerned about ratios than true weight. So long as you don't interchange units of measurements, it shouldn't matter what you choose.

[mike stenson]

Weight on a fluid ounce will vary by liquid. Kind of like a ml is a gram, only if it's water.

[Mike Cutler]

From the system 3 website.

"All System Three® epoxy products can be measured by weight or volume. Pourable products can easily be measured by volume, but paste and putty products are most accurately measured by weight. The correct mixing ratio for your product can be found on the product page."


I have used gallons of System 3 epoxy through the years, and unless something has recently changed, I have mixed it in epoxy cups, following the ratio. 2 parts resin: 1 part Hardner. I have been doing it by volume.

If you have the pumps, there are two sizes. One for the Hardners, and one for the resins. However, in the kit for the Resin Pump is a small piece of plastic tubing that is inserted inside the pump mechanism forcing it to short stroke if you want to use that pump for the hardener.
Always have two clean cups, as well as your mixing cup. Pump the resin into a clean cup until you have a solid stream, then pump however much you need into the mixing cup. Repeat the process with the hardener. If you have mixing cups, there are measurements to ensure you're getting the correct volume.
Once you're done, pour the clean resin, and hardener back into their respective containers.

[Richard Coers]

From the system 3 website.

"All System Three® epoxy products can be measured by weight or volume. Pourable products can easily be measured by volume, but paste and putty products are most accurately measured by weight. The correct mixing ratio for your product can be found on the product page."


I have used gallons of System 3 epoxy through the years, and unless something has recently changed, I have mixed it in epoxy cups, following the ratio. 2 parts resin: 1 part Hardner. I have been doing it by volume.

Unless the information I found is wrong, you are way over catalyzing.

[Mike Cutler]

Richard

That is the ratio on the System Three website for their epoxies. They may have epoxy formulas that are different ratio's, but for their "run of the mill" two part epoxy, it is a 2:1 ratio. West Epoxies are a much greater ratio. I believe just slightly over 4:1.
From the System Three Website;

"Dispense from the plunger pump or pour the Part A (resin) into a graduated mixing container, then pour the Part B (hardener) directly on top of the resin. Example to mix 3oz of a 2 parts resin to 1 part hardener product. Pour the resin (part A) up to the 2oz line, then pour 1oz of hardener directly on top of the resin bringing the total volume to 3oz."

" Technically", System Three does not classify their hardeners as a catalyst. We'd need a chemist to explain the difference. I can't.

[roger wiegand]

Just as in baking and cooking, measuring by weight is now faster, easier, more convenient, and more accurate. I have no idea why people mess around with liquid measures (especially of thick, sticky liquids) in these days of cheap, accurate electronic scales.

It's not a catalyst because it is one of the reactants and is transformed in the polymerization. A catalyst, by definition, increases the rate of a chemical reaction without being changed by the reaction.

[Kevin Jenness]

Epoxy mixing ratios can differ when measuring by weight and volume because resin and hardener may have different densities. Check the System Three specs to be sure. The guidelines quoted by Mike above indicate that the 2:1 ratio is by volume. I have been using a marine epoxy from Progressive Epoxy Polymers that is 2:1 by volume and 2.37:1 by weight. West System 105/205 is 5:1 by either weight or volume, while 105/207 and 105/209 are 3:1 by volume but 3.5:1 by weight. You can be a bit off and still get a batch to cure but accurate measurement gives the best result.

I usually measure by weight as I often want to mix a smaller batch than dispensed by pumps and it's easier to get an accurate measurement with a small amount. If using pumps it's a good idea to test for accuracy every so often, especially if you don't use them much.

[Mike Henderson]

I use West System for projects where I need a fair amount of epoxy. If I just need a small amount, I use those two-tube packages you can buy at Home Depot. That's always 5 minute epoxy.

Mike

[Andrew Hughes]

I also use west systems epoxy my can says 5 to 1 ratio. Some years ago I call west systems and asked if 5 to 1 ratio could be measured by weight. The tech said yes.
I have a small digital scale and have made up batches as small as 5 grams epoxy to one gram of resin. It’s not a precision process i usually waste more then I use making up the batch.
still figuring that part out.

[Ray Selinger]

System 3 bought out Industrial Formulators.System 3 got the Cold Cure and G2 epoxies.I have been using G2 and Cold Cure for a long time, always mixing by volume. When IF sold G2, you could vary the flex by varying the mix ratio. But now the bottle says only 2:1 .

Epoxy is pretty handy for woodworking, adding mini-fibers, carbosil,saw dust and colour Wooden boat builders have a lot to say on it's uses.

[andy bessette]

The 2:1 mix is fairly insensitive to small variations in mixing ratio, unlike WEST's 5:1. So you should be OK with using either weight or volume.