... 1000 words"

Here is a vivid example what happens to (red) chips in particular when left in vynyl holders and album pages that contain PVC.

The bleeding doesn't happen overnight, but after a long period of storage. The PVC flips are fine for short term use ... such as mailing chips as a protective measure, or transporting chip purchases home from a show for temporary safe-keeping in them, or for dealers to store them in for sale at chip shows, but they should not be used for long term use. Not only does the bleed onto the flip become noticeable after time, and the surface of the chip becomes "gummy" ... but the bleed onto the center inlay of the chip (as you can see) is all but impossible to remove.

Also; while not as noticeable, it's been my experience that when I've stored brand new chips with bold hot stamps in PVC holders ... where the gold hot stamp has weakened considerably over time while being stored in these type holders.

Personally, I like the fold over 2x2 or 2 1/2 x 2 1/2 white cardboard holders with acetate or mylar windows that are stapled in the corners (or sealed with tape or self-stick adhesive).

There are plastic flips that do NOT contain PVC which are suitable for long term storage, but some collectors don't like them because they are usually hard and brittle and crack at the foldover when handled frequently. Best bet when using this type holder is to put it away in your binder page or storage box and don't take it in and out frequently.