Follow supplier instructions.
Measuring by weight isn’t a problem for many. It is a good weigh (
) to get accurate quantities.
Digital scale IS a good suggestion.
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Graduations on mixing cups are often wrong/inaccurate and imprecise, making mixing by volume, especially low quantity batches, much more error prone.
Errors on ratio, or insufficient mixing od parts a and b, with epoxy, can lead to tool throwing curse fests.
I love thin viscisity epoxy.
System 3 Clearcoat epoxy was by far my favorite for laminating with near instant saturation of cloth, and deep penetration of wood, when it was easily available.
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All of the epoxy I have on hand (and several I’ve used up fully) have been volume only. I do have anmd use a scale but that is for silicone only since that has to use weight to mix it up.
So long as all your cups are wrong it isn’t an issue even with small amounts. Just need to stick to one cup maker to be safe. I often mix batches that are less than 100ml and have had no issues when using cups made by the same place and at the same time.
Trust me when I say I make a ton of tiny epoxy things on top of doing fiberglass work. Makes it nice since I can over mix epoxy for the fiberglass and then the extras go into molds so I don’t need to worry about not having enough.
this is bad advice
I guess we will disagree.
I have had much better results mixing 100:45 by weight (or :43, or :44) to nearest 0.1 or 0.01of a gram, than I have by mixing 2:1 by volume.
My biggest regret was not getting a digital scale sooner, and I am never, ever, going back to mixing by volume unless it is a travel scenario when traveling with a digital scale and milled fiberglass powder and cab o sil, might land me in jail.
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Yep, I use wee drug dealer scales for small amounts when gluing in inserts. And I owe the Mrs some new kitchen scales.
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me too
Read the rest of what I said. I said they need to be from the same manu and made in the same batch. If you want to be extra with it you could pour water in both cups and weigh them if you need the assurance that both cups hold the same amount at the same markers.
It is annoying to do which is why when I buy epoxy by the gallon I only buy from brands that have pumps with them. I do check that the pumps are pumping equal amounts but after that it is so much easier to just use one cup vs using two. Big jugs of epoxy are too hard to mix in the same cup if I’m pouring it in so I always have to use two cups so I don’t over pour the second part.
I do still have jugs that arrived yellow (ordered crystal clear) that don’t have pumps and they’re large and a pain in the ass. They did refund me fully so at least they were free and work fine for fiberglass. Just can’t use it for fancy pours
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I worked in a few surfboard glassing houses, where the dispensing pumps, had stems which had self drained enough, to screw up the ratios, and the laminators and fill coaters, too used to polyester resin, and sniffing their fumes, did not question what the pumps had dispensed .
One batch of boards, laminated and fill coated the day before my first day on the job, came out so wrong, the owner had to eat thousands and thousands of dollars, and the tantrum thrown, was one for the ages.
The pumps thereafter had huge dayglow signs, replaced regularly with angrier and insulting fonts saying:
Measure by Weight!!!
100:45, or be fired!!!
There was a stack of new digital scales right next to the drums, and the older polyester resin old school guys were not allowed to touch EPS blanks anymore.
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If I was working on a surfboard I’d def check the volume of both parts in separate cups which is the same as I do for fiberglass (partially because I have to but I’d still double check if I had pumps on those jugs).
If the ratio is slightly off when I’m making smol bois (basically decoration pieces) then it isn’t a real issue and at worst it takes an extra day or two to fully harden.
Also damn it sounds like you guys mix it up in huge batches at once if they managed to ruin that much epoxy.
Me 3.
Weight is easier, use a single cheap throwaway cup. Beats cleaning or replacing graduated ones.
I keep using the same cup, as long as the bottom is flat, and sides non lumpy, so the mixing stick can scrape them clean.
I used to hate to have to pour 10ml of resin, worrying about meniscus into a totally level mixing cup, then precisely add 5ml of hardener, hoping to hit the dead center of graduation, accounting for meniscus of different viscosity hardener.
Now Ill zero scale with cup atop, pour 11.44 grams, multiply by 0.45, hit tare button, and pour 5.15 grams of hardener, and have it come out perfect everytime in a fraction of the time.
Epoxy’s adhesion and other properties such as tensile strength are affected by ratio. Its not like polyester resin where the catalyst only influences the rate of cure.
3% too much or too little hardener might only reduce bond strength and tensile strength by 5%, and it will seem harden to sand OK., perhaps normally.
Been there, only later to find it did not bond well or broke, and when going to repair it, sanding through different layers, to find it obvious, by sight, and sound, that what I convinced myself was just fine a year or 5 earlier, was not.
Lesson learned.
I weigh my JB weld now.
When I first started weighing epoxy, I was pouring resin and hardener by volume into my preferred mixing cups atop the scale, just to see.
Whether the meniscus was touching top or bottom of graduation made a huge difference.
Never again by volume.
Not for me.
With JB weld, squeezing equal diameter and height blobs is a fantasy, the digital scale does not lie.
Ill never mix by volume again, if I can help it.
never never never.
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I’m going to have to start doing this by weight.