once again mma and gma users.  the difference in batch to batch depends
on the season and how much (hydroquinone, I believe) they have to put in
it to keep it from polymerizing on the shelf or while shipping.  I buy
the pure most pure gma (low acid) from polysciences in 5 gal. quanities
and store it in the cold, this way I know what is in it.  i have used my
stock gma stored in the cold for up to 4 years without any change in
it's performance.  i know you guys are talking about mma, but i am sure
the same rules apply.
patsy