: I use Raka. The density seems to be pretty close. I have not mixed a bad
: batch yet with one exception which I (on hind sight) may have mixed 1 to 1
: by mistake -- my fault, of course.

Raka's website does not list density information, and I have no independent knowledge of it. But the following is off their site:

"I want to emphasize the importance of proper mixing. Epoxy's strength and desirable properties come from the complete mating of the resin and hardener molecules in the correct ratio. Too little hardener produces brittleness, and too much hardener makes your epoxy softer with the accompanying loss of strength. If you make an error, you're safer to use a little less hardener, than too much. Generally speaking you can have a 20% error tolerance on the minus hardener side and 10% on the plus side and still get an acceptable cure. Regardless, your cure will have less strength than its ultimate potential!"

ra hardener does not speed up the cure, and it makes the epoxy weaker. The respective densities of the resin and hardener are listed on the Material Safety Data Sheets that were shipped with the product. Look under Section III - Physical/Chemical Characteristics, Specific Gravity. A simple calculation will convert from volumetric to weight equivalence, and your nifty scale will put you right on the money.