In article , ark@research.att.com says...

>In article <4jm9vg$2nq@newsstand.cit.cornell.edu> d_ruether@hotmail.com (Bob Neuman) writes:

>> - One filter brand seems to acquire a haze spontaneously (Tiffen).

>Haze on filters is usually the result of the use of vinyl
>in the storage container.

Yes, I just checked my two Tiffen filters (CC30M - I put the Tiffen glass in thinner rims so they will fit Nikkor wides without vignetting)
which are stored in Nikon plastic filter boxes, and they were not hazy
(they often are when stored for a while in Tiffen boxes), so your
explanation seems reasonable as a cause for the hazing I mentioned.
Thanks.
Hope This Helps