: The epoxy and hardener will have different specific gravities so
: the ratio when measured by weight will not be the same as the
: ratio by volume. Make sure you have the correct ratio for your
: preferred measuring method.

That's what I think I said or at least meant - The weight ratios are also usually given on the bottle. I use West Systems and they give
To measure 105 Resin and 205 or 206 Hardener - by weight or volume -, combine five parts resin with one part hardener.
To measure 105 Resin and 207 or 209 Hardener - by volume, combine three parts resin with one part hardener
- by weight, 3.5 parts resin-1 part hardener - I usually then make it seven to 2 and multiples of that for ease of operation. (I know the 7x table :-)
The 2 plastic cups method isn't as accurate as weighing and I find it slower. I use a sauce (ketchup) bottle to dispense the resin and hardener - something I learned here.
The weighing method I also learned here, but it was on a balance beam. My wife's electronic kitchen scales seemed more efficient.
Cheers
JohnK