Looking for a water resistant 'sandbag'

["Bill and Rudi Weissinger" <weissinger@zzzzzzzzzzzzzz>]

For water-resistant sandbags, I've seen sculptors use tire inner tubes, cut
to size and tied off in a way similar to what Don recommends.  I haven't
tried them myself -- I fear the black may rub off on my work.  But those who
do use them report no ill effects -- but then, I didn't ask.  Perhaps
someone in the group has tried them?

Reportedly, the nice thing about having a water-resistant material like
plastic or rubber for the bag of your sandbag is that the bags can be rinsed
down easily between "grit" stages in the sanding process, so that your work
isn't scratched as you move up the grit scale by coarser grit clinging to
your sandbag.  Personally, I use tied-off blue-jean legs, and my defense
against coarser grit hanging around as I move up the grit scale is
(sometimes unwarranted) optimism.  I'll try Don's plastic-bag idea as more
reliable than optimism, but if anyone has tried tire inner tubes, I'd be
curious as to the result.

Bill Weissinger