I guess I should clarify for those that don't know what we are referring to with pumps, measured cups or weight scales.
Pumps are nothing more than plastic mustard pumps used at hot dog stands to dispense mustard. They thread onto the plastic jugs and protrude into resin and hardener. Some companies like Wests System, the pumps are metered so one pump of resin gets one pump of hardener even though the mix ratio is 3 to one.
Other companies such as Raka use the same pump metering for each part of the mix so it takes 2 pumps of resin and one pump of hardener for their 2 to one ratio.
For many years, I just used the pumps and trusted they were accurate. However, I always ended up with extra resin or hardener when everything should have been used up. I always attributed it to they just didn't measure what they sent me, accurately.
I started not trusting the pumps accuracy and I started pumping the resin and hardener into a cup with accurately measured lines on it. Actually it's double cup, one with lines one for the mix. Low and behold the amount left after all should be equally gone from the original jugs was much closer to what it should be.
Then I started using a gram scale to measure by weight rather than volume. Again I still use the pumps, but now I pump into a cup exactly the amount I need of the resin, and pump correct amount of the hardener by weight. This method has proved so accurate that I now expend the same amount of resin and hardener at the end of the jugs so there is little or nothing left in either container.
The bottom line at least for me is being able to use the pumps to dispense the product is great. However, I don't trust the pumps to accurately deliver the correct amount every time. When the pumps set for awhile, the first pump is a primer pump, and tends to burp air which is not giving an accurate measurement. Epoxy that is not measured accurately will either be soft or brittle. At dollars per once and the risk of ruining a project, I needed to find a solution.
Pumping into a measured double cup is very accurate, but you are limited to pre-set amounts marked on the cup.
The Gram scale gives me the ability to measure the tiniest amount to any amount I need with the greatest accuracy. I routinely mix 1/4 oz. or less for different projects.
If your just doing one project such as a TTT the so called metered pumps are probably all you need, but if you frequently use epoxy for many different projects, from big to tiny, you might consider weighing your epoxy with an inexpensive gram scale.