A few things

[David Paule]

Concur with n8zg, good advice about the scale. Also have a calculator handy, of course.

And don't forget to zero the scale once the cup is on it.

I've gotten decent digital kitchen scales with .1 or 1.0 gram resolution at Bed, Bath and Beyond, and they frequently run 20% off coupons.

[tomcostanza]

What "by weight" ratio do you use?

[Tony_T]

West Systems sells, recommends, and supports the ratio pumps. I don't see how you can go wrong using them; and they are very convienient.

One thing that comes to mind regarding the epoxy not hardening is the type of cups used. It is possible that some cups have wax or something on them that could contaminate the mix. Just a thought.

Tony

[DanH]

Originally Posted by tomcostanza

What "by weight" ratio do you use?

West is 5 to 1.

No pumps for me. I don't even use them to refill the cheap squirt bottles used to dispense resin and hardener into the cup.

Go ahead, try to mix an accurate 12 gram batch of West with a pump. Then mix some T-88 or Hysol.....

A scale ratios any epoxy perfectly, including those too viscous to pump.

[Dave Cole]

Originally Posted by Tony_T

West Systems sells, recommends, and supports the ratio pumps. I don't see how you can go wrong using them; and they are very convienient.

I attended an RV Fiberglass forum given by Sam James at Oshkosh. He also endorses and wholeheartedly recommends the pumps. Yes, you have to be sure they are primed. But after that, they are really simple to use without making mistakes.

I used to always use scales when mixing epoxy untill I tried the West Systems pumps, and I see no need to go back to scales. Scales are accurate, of course, but there are so many ways to make mental mistakes that nullify that accuracy.

[joedallas]

Both methods are good if executed properly.
I used both and I prefer Scales as I know it is exact
Some Like Fords and some like GMC.

If you aren’t sure of your Ability use both

Joe Dallas
www.joesrv12.com

[miyu1975]

I had the exact same problem....I then realized I had the wrong pumps in the wrong containers... I switched the pumps correctly....perfect now.

[David Paule]

Originally Posted by tomcostanza

What "by weight" ratio do you use?

The weight and the volume ratios are given on the containers. They vary with the particular hardener.

With the pumps, you need to ensure that they are working properly. Often the first stroke is a partial load. Hate to say this but sometimes it's worth wasting a couple of small paper cups, one for the resin and one for the hardener. Put the first stroke or two in the cups and when you're sure that the pumps are working right, use your mixing container. Then pour the other two containers back in their respective cans - little waste except for the cups.

[joedallas]

Originally Posted by David Paule

The weight and the volume ratios are given on the containers. They vary with the particular hardener.

With the pumps, you need to ensure that they are working properly. Often the first stroke is a partial load. Hate to say this but sometimes it's worth wasting a couple of small paper cups, one for the resin and one for the hardener. Put the first stroke or two in the cups and when you're sure that the pumps are working right, use your mixing container. Then pour the other two containers back in their respective cans - little waste except for the cups.

Why not use the pump in one cup then weight it and if it's the sum of the weights it good to go.
The main drawback is the batch size.

Record the results to see how accurate the pumps are or aren’t.
Joe Dallas
www.joesrv12.com

[JohnF]

West replaced the epoxy and activator when the product refused to harden; and provided a replacement set of their mini-pumps. They paid for shipping to me, and shipping to return the stuff that would not set up after days.

Today they called me and said the epoxy and activator that I had returned was OK, but the paper cup I sent them with some of the epoxy that would not harden was analyzed by their chemist and they determined that excessive hardener was added to the epoxy. I cannot determine how that happened since I have used West's epoxy before, and also since the incident and never had any problem. I can only guess, and its a wild guess, that somehow the mini-pump malfunctioned.

I am very pleased how West responded to my complaint, and how they followed up after determining what happened. A good customer relation act.