Ron,
I am using an Ohaus Scout scale and do not experience the
problem you describe. Cost was under USD100 a few years
ago.
My scale certainly appears to accurately show the addition
(or removal) of each drop or two of resin/hardener. Even if
I stop pouring for a while and then proceed with the
addition of resin/hardener, I experience no problems.
I also carefully watch the display as I add resin and would
notice immediately if it did not read zero when I started
pouring. I guess if one were to start pouring before
looking at the display, then the problem you describe could
result.
I agree with keeping the mixing sheets separate so that you
don't confuse the two. I took a moment and used MS Excel to
produce mixing lists ranging, in half gram intervals, from
one to two hundred grams (the limit of my scale). I also
printed the redux list in a bluish green (redux) color as a
visual reminder. My list is three columns wide -- resin,
hardener and total.
I utilize a plastic 1 liter squeeze bottle for the resin and
a smaller squeeze bottle for the hardener. When I pour the
resin from the larger bottle, I don't attempt to pour an
exact amount. For example, if I need to mix up a 75 gram
(approximate) batch, a quick glance at my spread sheet
shows I need to start with 59 grams of resin. I then pour
in resin and stop when my scale reads something close to 59
grams. If it reads 61.2 grams, I don't pour any back, I
simply dip a little piece of cut-up paper towel into the cup
and wick out a drop or two until the scale reads 61 grams.
I then lay a ruler on the 61 gram line as a reminder of how
much resin I have in the cup. I then note on the sheet that
for 61 grams of resin, I need to add hardener until the
scale reads 77.5 grams. The smaller squeeze bottle is
fairly easy to control and I simply squeeze in the hardener
until the display reads 77.5. If I happen to add an extra
tenth of a gram or so, dip a paper towel wick into the
"puddle" of hardener sitting on top of the resin. I am quite
convinced that when "wicking" hardener, I am not also
wicking out any resin.
I imagine that a carefully maintained epoxy mixing pump
would be faster and more convenient than my method, but
after reading about the problems some people have had with
the accuracy of their pumps and the maintenance issues, I am
satisfied with my decision to use a scale.
A hint on mixing small batches of redux: put a clean mixing
stick in the cup before you tare the scale. Then use that
mixing stick to scoop out some of the thick redux resin.
You can now leave the stick in the cup while weighing the
resin. The alternative is to scrape the redux goop on the
lip of the cup but that is messy and harder to mix as the
resin in on the top and sides of the cup and runny hardener
ends up on the bottom. If I find I need to remove a bit of
the resin, I use a small piece of stir stick (about the
width of a small screwdriver blade) to scoop out a tiny bit
and scrape it back into the bulk container. If I need to
add a bit of resin, again use a small stir stick to scrape a
bit more onto the large stir stick already in the cup. Next
step is to add the hardener, which I seem to be able to
accurately pour straight out of the bottle, but again, if
you end up with a couple of extra drops, just wick it out
with a paper towel scrap.
Cheers,
Bruce
XS A142
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