Epoxy ratio verification method

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jbo_c
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Epoxy ratio verification method

Post by jbo_c »

No rocket science here. Just what I’m doing. Since I obviously mis-measured a batch back in the fall and caused myself a lot of extra work and no small amount of consternation, I came up with this verification method.

I bought 300 clear cups for mixing and marked one in pumps and one in batches. Now, every batch I “pour” goes into a fresh cup, which can then be dropped into one of these to make sure it’s “correct”. If I know which product was off - like the pump burped toward the end of the bottle, so I know I didn’t get a full pump - I can be comfortable I got the amount corrected.

I’m sure many people have their own methods that work for them too. Maybe this gives a “new guy” an idea.

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bklake
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Re: Epoxy ratio verification method

Post by bklake »

I do something similar but for oz batches, no pumps. I'm sure you did this because your gauge cups a clean but to make sure. Drop a fresh cup into a cup that is be the gauge cup. Mark the gauge cup with a fresh cup inserted. Keep the gauge cup clean and unused. There is a difference in the level if you don't do this.

jbo_c
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Re: Epoxy ratio verification method

Post by jbo_c »

Yes. First measure needs to be with a cup inside the “measure” cup.

Jbo

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Re: Epoxy ratio verification method

Post by bklake »

I had a look at my cups and my method is a little different. I use them to measure batches rather than verify pumps. When I saw this method described, it didn't make sense until I set it up and tried it with all the parts and pieces in front of me. Sorry if I am running on with this.

I have a kitchen scale that measures to something like a tenth of an oz. Being a kitchen scale, for the kitchen, that my wife likes to use, I can't press it into service in the garage. I put two cups on the scale and hit the tare/zero button. Then I added water to bring the weight up. 1.5oz of water seemed like a good amount in the cup for a small batch of epoxy. I put .5oz of water in the cup and marked the line as B on the outside cup. Then I added 1.0oz of water to bring the total to 1.5oz and marked the line part A/Total. The cups are tapered and .5oz comes up higher in the cup if it is first. The ratio looks wrong if you measure and mark the cups part A then part B. The math says it is correct but it looks wrong. I know it is out of alphabetical order. I don't lose any epoxy that sticks to the cup when poured together. One cup wasted per batch not two. I made cups for bigger batches using the 2:1 ratio of water. I don't know exactly if it is 1.5oz of epoxy by volume but what is in the cup is appropriate for the project at hand. Water is the same weight so it works for making volume measured mixing cups. Put two cup together with the "scale" cup outside. Pour in the B to its line. Pour in the A to the top line. Stir. Make boat parts.

The biggest batch I can comfortably mix in a 16oz cup is about enough epoxy to do about 2sq/ft of 12oz biax. Could be wrong on that, I was working fast and didn't really measure the area covered.

Dougster
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Re: Epoxy ratio verification method

Post by Dougster »

Seems like that would be a two to one mix by weight, not volume :doh: I don't recall what the mix by weight ratio is though.

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jbo_c
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Re: Epoxy ratio verification method

Post by jbo_c »

You’re right Dougster. Weight ratio is slightly different. Can’t remember exact, but not quite 2:1. (Though before I knew I mixed that way and never had any problems. Holding my mouth right, I guess.)

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Re: Epoxy ratio verification method

Post by Jaysen »

Well… there have been discussions in detail about this. This being weight vs volume mixing vs guess work. Short answer: find a method that works and have at it. Just remember that at 2:1 you have a lot of room to be off a bit compared to 5:1 (west) or 50:1 (ester).

Don’t sweat anything more than keeping straight which is resin and which is hardener. And the ratio. I guess that is important too.
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Re: Epoxy ratio verification method

Post by OrangeQuest »

BBC's brand of epoxy is a 2:1 ratio and is sold by volume and not weight. The weight ratio is 100g to 44g. If you use the weighing method to mix epoxy you should have a little resin left in the gallon jug when you run out of the half gallon jug of hardener.

Everyone needs to use a method they are comfortable with.

I like using a scale so I can quickly measure, mix and use. easy to use different mixing containers and calculate different amounts of mix.
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bklake
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Re: Epoxy ratio verification method

Post by bklake »

Dougster wrote: Tue Jun 06, 2023 9:30 am Seems like that would be a two to one mix by weight, not volume :doh: I don't recall what the mix by weight ratio is though.

Dougster
I knew this would come up and it tripped me up at first. I calibrated the cups with a water which is a constant weight. 2oz of water will have twice the volume of 1oz of water. 2:1 ratio. The weights of part A and B are different but I'm not weighing the epoxy, I'm pouring in a volume of epoxy to a set line on my calibrated cup. The water and scale were only to calibrate my cups. The epoxy and scale never meet, as directed by my wife.

Sometimes I have the attention span of a 3 year old with ADHD. I can't count how many times I lost track of pumps when I used those. Two lines on a cup has been much better for me.

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Re: Epoxy ratio verification method

Post by TomW1 »

As far as I am concerned pumps are inherently inaccurate, you need to apply the same amount of force and speed to each pump to get the same amount of fluid each time. Using cups and other measures like spoons it is easy to mix. For large batches 2 red cups and 1 blue cup of the party cups. For smaller batches I buy plastic measuring cups and use them, 1c-1/2c, 1/2c-1/4c, etc, or whatever multiples you need and use tongue depressors to get the epoxy out of the cups and wipe them out between batches.

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