Digital BW, The Print

After letting  2200 prints (on Epson paper) dry for several days and 
then, matting and framing, I notice a film deposit under the glass 
that matches the image. It happens in as little as 3-4 weeks and 
really dulls the appearance of the photo(b&w or color)and must be 
cleaned. Forced drying helps to greatly reduce this problem. 

I have seen this problem with older ink jet prints also. Any thoughts 
on this?
Ron