What is the best way to store old magazines, that you know aren't acid free?

[lastlib]

5. here's something that works for newspapers.

sandwich them between two pieces of cloth (white muslin or cotton, no colors (the dyes may bleed into the paper)) and roll it all up in aluminum foil. Store them in a dark dry place that's reasonably temperature-controlled. They'll keep this way for a good long time.

I did this with copies of our city paper's editions from the Apollo 11 moon landing (1969) and unwrapped them four years ago (forty years later). They looked like hot off the press.