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Epoxy Scale

I just went on amazon and bought a scale that would measure small amounts. I have the pumps that west system sells and they work great but often that is more than I need. I calculate the amount needed and simply weigh out the amounts in a small.cup using the scale to get accurate amounts.
 
john lucas said:
I just went on amazon and bought a scale that would measure small amounts. I have the pumps that west system sells and they work great but often that is more than I need. I calculate the amount needed and simply weigh out the amounts in a small.cup using the scale to get accurate amounts.
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What scale did you get on Amazon
 
There are plenty of digital scales that work fine for measuring chemicals, I have used a cheap harbor freight digital scale for measuring
dry and liquid chemicals in one of my other hobbies for about 10 years and it still works fine. You just need to make sure the scale has a
zero function so that when you place a cup or bowl on the scale you can zero the scale.
 
lots on Amazon or Ebay-- get one accurate to 0.1g for small quantities. 0.01g is better (they are never actually that accurate) but unless you pay a lot the capacity will be much less. Get one that can be calibrated, if possible. Always check to see that they are giving results that are close to right before use. A nickel weighs 5.00 g, so that's a convenient thing to use for a check (pennies since 1983 weigh 2.5 g) For this purpose consistency is much more important than absolute accuracy, so check that a few nickels give you the same weight several times in a row. I've found the cheap (<$20) balances to generally be good to +/- 2-3%, which is fine for epoxy.
 
How acurate does it have to be? I have not used quantities greater than 1 oz but got that just make equal size puddles and mix. Now why not use volume measure instead of weight? It is much easier to get equal volume in measuring cups than all that fussy weighing and being a Pharmacist I am trained to do both.
 
Well, I guess you should do whichever you're comfortable with. I've always had trouble accurately dispensing small amounts of viscous liquids by volume, you pretty much need a positive displacement pipette (which is what the metering pumps provide for larger volumes). I like to mix epoxy in a throwaway small paper or plastic cup, these are tapered in shape and nearly impossible to accurately guess even a 1:1 ratio, much less a 1:2 or 1:5 that some of my epoxies use. Measuring in a small graduated cylinder would present a problem of mixing and differential loss of the two components. Weighing seems to me like a vastly quicker and easier way to get where I want to go.

Perfect accuracy certainly isn't required for this, but I've had many fewer instances of epoxy that took forever to set up since I started using the little scale in stead of the "equal puddle" method. It only takes about 15 sec longer, the time to grab the scale off the shelf.

In the lab I had $1500 pipetting devices to allow me to accurately and quickly dispense small volumes of viscous liquids by volume, that's an extravagance I can't afford in my shop. Even then, if it had to be right (by which I only mean <0.1% error) I'd dispense by weight rather than volume.
 
Gerald Lawrence said:
How acurate does it have to be? I have not used quantities greater than 1 oz but got that just make equal size puddles and mix. Now why not use volume measure instead of weight? It is much easier to get equal volume in measuring cups than all that fussy weighing and being a Pharmacist I am trained to do both.
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This is how I have always done it. I just use mixing cups from Lee Valley and haven't had a problem. I might be wrong but I thought Wests states to mix by volume?
 
When I was in the boat building business decades ago we would use Dixie paper cups for small quantities of polymers and catalyst. Wooden stir sticks were also cheap and disposable.
 
mixing by weight is dead on accurate. With West system hardeners you have to mix at different ratios so you can't just mix 50/50. I think they are 5/1 and 3/1 if I remember correctly but that's just with the ones I use. Other brands and probably even other products from West system I'm sure mix at different rations. 1 minute and 5 minute epoxies in syringes are probably more forgiving so getting them close to 50/50 is probably good enough
 
I use pumps like these for 1:1 bar top epoxy. Before, I was having trouble measuring small amounts for inlay, etc. The only problem arises if your shop is unheated. Cold epoxy has the consistency of concrete, but that would be aproblem for any measuring method:

https://www.amazon.com/NiceBottles-Dispenser-Pump-Gallon-Pack/dp/B00XLXYM8O/ref=sr_1_5?hvadid=241929372626&hvdev=c&hvlocphy=9012797&hvnetw=g&hvpos=1t1&hvqmt=e&hvrand=868954319165001878&hvtargid=aud-647846986441:kwd-1074804900&keywords=epoxy+pump&qid=1556494369&s=gateway&sr=8-5
 
Based on rod building epoxy which is fussier than adhesive epoxy:
If you're mixing small amounts of epoxy (2-5 ml total) syringes work well and are accurate enough. You need silicone free syringes if you care about the surface appearance of the result.
If you're mixing very small amounts (1-3 ml total), just count drops. It takes 20 seconds for each part to drip out and some practice to learn the angle you need to hold the bottles, but you get perfect accuracy.

Rod building epoxy is intended by the manufacturer to be mixed by volume and not by weight. (the densities of the 2 parts are not the same) Not sure if this holds true for the types of epoxy under discussion here.
 
Both West and System3 (the ones I've primarily used) provide both weight and volume mixing ratios in their literature (which differ because the densities of the components differ), so you can take your choice. I'm pretty sure they'd prefer you just give it full pump each time, no matter how much you actually need, so they promote that system. One pump of each is also a more foolproof system, so fewer complaints of failure resulting from math errors.
 
Like Gerald mentioned previously, I will second the volume approach. I use dirt cheap portion control plastic cups. You can buy 1, 2, 4 oz and so on. Pour into each, blend and discard.

Also, just a quick mention: If you're using the Enviro-Tex products, they specifically warn against weighing and use a 1:1 ratio by volume. I don't know if a lot of you use / have used the product. I have used it quite a bit as a "liner" for vases I've made and it works very well for that purpose.
 
Roger Wiegand said:
Both West and System3 (the ones I've primarily used) provide both weight and volume mixing ratios in their literature (which differ because the densities of the components differ), so you can take your choice. I'm pretty sure they'd prefer you just give it full pump each time, no matter how much you actually need, so they promote that system. One pump of each is also a more foolproof system, so fewer complaints of failure resulting from math errors.
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I like the West pumps but only use that epoxy when I need a lot. It would be nice if they were to offer a 1/2 volume pump set to the normal pump set. Could be color coded so as not to mix up the two pumps. For most of my needs, the Loctite 4oz bottles are easier to measure smaller quantities. For really small, the Loctite double-barrel syringe works fine.
 
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