Widely found and used to store documents with other memorabilia, PVC clear plastic sleeves are a definite NO to any family historian. The number of people who approach me at Family History Fairs with old and fragile original family documents (certificates, wills etc) in PVC sleeves is astonishing. What is more surprising is they are not aware of the long term damage PVC can cause to their precious documents.
PVC has plasticisers added that make the PVC soft and pliable. These plasticisers over time migrate into the document and destroy the print and also eat into the paper. You will have seen examples of this when you try to remove a long term stored document and the PVC sleeve is sticky and has some of the print transferred from the paper onto the plastic.
The archival way of storing your documents is to use acid free inert PP (Polypropylene) or PET (Polyester) sleeves. These two are widely used by professional archivists to ensure safe storage of valuable documents and memorabilia. PP is by far the most common type used mainly because of availability and the lower price. The benefit of using PET (used by more professional bodies) is the ultra clarity and generally more lightweight gauge of sleeve.
At Family Tree Folk we stock a wide range of PP sleeves in A4 portrait, landscape and photo sections as well as the longer foolscap certificate size PP and PET sleeves. If you want more information visit our website at http://www.familytreefolk.co.uk/ or contact us for advice.