Framers and others in the art industry use the term "acid-free" loosely without knowing its true meaning; or in an attempt to sell you inferior products that will destroy your framed items to make more profit. Framers and framing companies are notorious in selling and using inferior products because they know that most will not know the materials and/or will never open their frame to see what is inside.
Acid free means no acid, the absence of acid i.e. A pH level of 7 (may be slightly higher (alkaline) for preservation framing applications). Examples of some acid free materials are:
Over time, light, heat, and other environmental factors will react with the acid in the framing materials causing deterioration and decay. Once this happens, it is virtually impossible to reverse the damage — even by a professional conservator.