I suspect that one does not need it to harden size or gum but if you make
up gum from powder, it will likely sour in a month or two so it needs a
preservative. From my experience it is the dirt in the gum that is the
culprit. Industrial bottled gum has been filtered pretty thoroughly,
possibly in some cases through a charcoal filter which I would suspect is
the case in any "white" gum. These are probably immune to fermentation or
have some other preservative in them. I used to make ammonium citrate
developer in liquid form from technical grade chemicals and it would grow
mold if I didn't filter it through a charcoal filter.
I've also had good luck preserving things with swimming pool algaecides.
Presumably reasonable safe since one is expected to put it in the pool and
then swim in it.
Thanks for the tip
Bostick & Sullivan
PO Box 16639, Santa Fe
NM 87506
505-474-0890 FAX 505-474-2857
http://www.bostick-sullivan.com