A tale of epoxy resin, carelessness, and a "save"

[angib]

Yep, it's worth stressing:

- With polyesters, which includes Bondo, you can alter the hardener ratio within quite wide limits to alter the speed of cure.

- With epoxies, if you get the hardener ratio wrong by a fairly modest amount, either way, the resin doesn't go off. If you want a faster or slower gel time, you have to buy faster or slower hardener.

If epoxy doesn't go off, and you think you used the right mix ratio, and you think you mixed it thoroughly*, it can be that the resin hasn't got hot enough to cure, so adding a local heat source can get it started.

*Mixing epoxy means stirring for the recommended time and getting the stirrer into every crevice of the mixing pot. By comparison, just waving a stick anywhere near the mixing pot is good enough for polyester.

[Miriam C.]

Ah well! So much for takin the thinkin out of it huh! Looking forward to the finish!

[Larry C]

Doesn't Raka have a metered pump system? The West system is 1 pump of resin...1 pump of catalyst, the pump bodies meter the correct amount. Doug

Doug,
Some here don't realize that some epoxy suppliers such as Wests use pumps that are metered by using different size pumps or a short piece of plastic tubing to make one unit pump less than the other (hardener).

This is especially useful for people that are not paying attention. It takes the guess work out of a sometimes frustrating rush to keep up with all that's going on. Wests, and others took care of that! One pump from each= the correct mixture (or close). No counting pumps is necessary.

Raka, just uses the same type and size pump for each which are really nothing more than mustard/ketchup pumps used at "hot dog stands"metered to deliver 1 oz. (more or less). They require a 2 to 1 pumping ratio.

After using all the different epoxies, and seeing what these cheap plastic pumps actually deliver has taught me to never trust what they do deliver.

Many years ago I stopped trusting the accuracy of these pumps. I weigh every mixture on a scale. It is as exact as one can possibly expect. I don't have to guess what I have when one of the pumps "burps" air which they all do from time to time. I still use the pumps with the burp and all, but into a cup resting on a digital scale. BTW/ Raka's mix by weight is 100 to 44.

Larry C