Thanks Paul! I'm thinking of a balance beam, with marks at the proper ratio on the weight end, using cups for both ends. Then, I'd zero it with empty cups, fill the weight cup with as much water as I want the mix to be, and set it on the hardner mark. Fill the mix cup with hardner to balance it, then move the weight cup to the total mix mark, and balance it with resin. Or vice versa and pour the resin first, as I always have with the measuring cups, but I read that by weight if you pour hardner first, then one or two drops off only has half the error margin, so I'll do it that way. In theory, I should be able to get batches of a few drops. Really, about 5 mg is the smallest batch feasible to stir good.

Then I can experiment with different batch sizes, and eventually I'll get to where I dont mix any more than I need. The site I saw had a simple wood balance beam, and said it should be accurate to .01 oz so long as there is no friction in the bearing. I thought I'd eliminate the bearing by using a pivot point. I could make the beam so that it would hold a splitshot anywhere along it, for your 'close' indicator.

: Hang an additional small weight on the side of the balance beam that you pour
: your resin or hardener into. When the beam starts to tilt you are close to
: the exact amount. Remove this weight and add enough, slowly, to reach your
: desired amount. A fishing tackle box should yield enough weight --
: anything from a few pieces of split shot to an old lure. Dull fishhooks
: with the barb removed are easy to hang and remove from your balance beam.

: If you want to get fancy, "calibrate" your balance beam by marking
: it along the length of the balance arm. Align your weight(s) at various
: places along the length, depending on the amount of resin you are mixing.
: If you are mixing a small amount, the weight will be closer to the center
: of the beam, and for a large quantity you move the weight further to the
: end. Just make a few marks at appropriate locations.

: My scale for reloading shotgun shells has a small, weak, flat, spring under
: the side of the balance that has the weight. As the amount of gunpowder on
: the other side comes close to matching the deisred weight the spring
: gently pushes the weight side up a small amount. This movement gives an
: indication that you are approaching the desired weight. You pour a bit
: more slowly after that to get the precise amount. You might try adding a
: spring beneath your balance beam to do the same thing.

: Electronic postal scales are reasonably priced at discount stores and office
: supply stores, and have accuracy to 1/10th of an ounce. Mine weighs items
: to over 64 ounces, as I found when I tried making a prototype
: Greenland-style paddle from a particularly heavy and dense fir 2x4. The
: rough cut came in at 64 ounces. Next time I'll spend a few cents more and
: buy a cedar 2x4 for the real paddle.

: I have a small pocket scale for mail which I picked up years ago at the local
: postoffice. It is a simple device that looks like an artist's French
: curve, with a hole in it to suspend it, and a wire for a plumb bob hanging
: down to indicate the weight. It should be simple to enlarge something like
: this and cut it out of a sheet of particleboard or 1/4 inch (or thicker)
: plywood for measuring the amounts of resin. carefully measure one batch
: and mark the scale in the right places. As the amount in your cup gets
: close to what you need the plumb bob will show it. There is a picture of
: this below which you can use for a guide, but I doubt the exact shape is
: important. You can probably cut this freehand with a sabre saw. I think
: something about a foot long, overall, should be good for most large
: batches of resin.

: PGJ