This article is from the Food Preserving FAQ, by Eric Decker firstname.lastname@example.org with numerous contributions by others.
Marie Martinek wrote:
I put my circle of waxed paper *inside the jar*. So it keeps the powdery
stuff from sucking up into the space between the jar and the lid. Which, of
course, also keeps it out of the pump parts.
Ross Reid wrote:
I put a wad of cotton batting (actually a single cotton ball) up inside
the recess in the very top of both my jar adapters. The cotton is held
there by a very narrow strip of Scotch\u2122 tape. I've never had flour or
anything else get past the cotton and the vacuum still works as well as
if the cotton wasn't there.
Eric Decker wrote:
Test jars done to the methods given here fail. The vacuum held for a couple
of months but one by one all twelve test jars lost the seal. The seal at
process time was solid. A test removal at process time deemed the FoodSaver's
vacuum was adequate. Unfortunately a microscopic level of flour must have been
present in all instances. There appears to be no way to guarantee flour will
not contaminate the lid. The curent reccomendation is: Do not use vacuum
sealing in glass jars for flour. Vacuum bagging flour is effective for
those who buy flour in large quantities at infrequent cycles and have a
need to exclude pests. Sugar and other higher density, more coarse,
items should continue to do okay.