I don't know what kind of plastic they use to make Tupperware, but I
would find out before storing prints in it. Some vinal plastics are
OK. Certainly Mylar is archival. But some like Polyvinalchloride (PVC)
are bad news-very bad news. PVC is unstable and with time will decompose-
one product of which is HCl.
Bob Schramm with his archivist hat on.