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Measuring Epoxy

Although these tips are directly related to the new W17 trimaran, they may also prove useful for those building other plywood boats.

There are already 32oz graduated containers for mixing large amounts and then the dispensing pumps for mixing very small amounts, but it often seem to me that one is too big and other too little and too slow!
To complicate things, 'measuring, mixing and using' are not very compatible with each other because to measure accurately, you would ideally need a tall vertical sided container of say, spray-can proportions. However, to mix and work from, it's easiest with a shallow, wide mouth container with some slope on the side and a smooth flat bottom.

Well, here's what I've found works best for me; so wherever you are working around the globe, try to find something close and give this a try. Could make your epoxy mixing a whole lot easier!

I have found that certain 100g Yogurt containers have parallel sides—and those used by ACTIVIA™, also have labels that conveniently have a white label of nutrition facts that give a perfect line at just under 23 full. So if your epoxy mix is 2:1 like some popular ones are, you simply pour in resin to the top of the white label. Then you add hardener to 5 mm from the top—easy to estimate—and you've quickly and accurately got the right mix.
Of course, you're now too full to mix it here, but you don't want to anyway. So just pour the whole lot into a soft margarine container that is ideal for open mixing and adding in your filler, and you're all set!
The fact that Activia yogurt is also delicious and claimed to be healthy is a side benefit of course and as I typically have one small cup a day and therefore get over 300 containers a year—I have plenty for ANY project! A 1 lb (454 g) soft-margarine (or similar) container will easily hold 3 yogurt cups (~12 oz) and is easily cleanable and hence reusable to last a week or so before switching to a new one. Just use the straight side of a Popsicle stick or tongue depressor to scrape the sides of the yogurt cup clean as you empty it. As they are nice and straight, it's quick and easy. Then scrap the small container—at least it was recycled once ;-)

If you want a smaller quantity, you can use the bar code lines on the side.
Typically they have a numbers like 0 568193 and on mine, the '1' is just 23 of the way to the top of the white panel. So add resin up to #1 and then hardener up to the top of the white panel and you'll have a mix of just 23 of the container (~3 oz). So check your chosen container with a measuring tape and find a marking that works for you!

If you're using a 1:5 mix, as for WEST System, there are also existing lines on the small container to guide this mix too. 5 mm from the top is 50 mm above the bottom, and the initial '0' of the bar code number is right at 10 mm above the base. So in this case, add the hardener first up to the '0' and then add the resin up to 5 mm from the top, before throwing the mix into the larger container for mixing, as noted above.

If you're worried about accuracy, then don't be. Using this form of measurement, unless you're VERY careless, is more accurate than using the pumps. Frequently, I find that resin pumps do not fully rise to the top of their stroke and therefore you can get a hardener-rich mix that does not cure as timely or as strong as it should—so watch for this! Also, as either liquid gets low in their main containers, there's a significant risk that the pump will not get fully primed, so be aware of this too.  


When mixing with added filler, for filling corner fillets and similar, pre-mix the epoxy first of course, but only mix a quantity equal to about 1/4 of what you estimate will be needed in volume to do your job.  The filler (especially silica, like Q-Cell) adds enormously to the volume and as the thickened mixture also starts to cure faster than the basic resin, you will save loosing batches of expensive materials if you start with a small quantity of resin first.    Just 1/4" (6mm) in one of the Activia containers shown above, will make at least 1/2 a container of white filler once you add the silica ... a little less if you are using the high density WEST #404 for a high strength joint.     Add the filler in stages and stir well to keep a check on the consistency.    You're aiming for a 'creamy peanut butter' mixture, just thick enough to not run out of the joint you're making.

Happy mixing!

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