Preservation framing has become increasingly important because of the increasing acidity of papers and pollution of the atmosphere. Most papers are made from wood fibers and are more or less acidic, and, upon exposure to ultraviolet light and acids in the air or acids in objects placed near them, become even more acidic and turn brown and brittle.The "cheaper" the paper, the quicker this happens; everyone knows a newspaper turns dark and brittle very quickly. At the other end of the spectrum are "acid-free" paper products, either made of non-wood plant fibers like cotton or linen (hence called "rag") or of alkali-buffered wood pulp. Using these products in producing, framing, and storing art will preserve the art for the longest possible time.

The framer can help primarily by surrounding the artwork -- front, back, and sides -- with acid-free materials. If you want to preserve works on paper for many decades, then, you should use acid-free mats and backings.

Strong light, especially ultraviolet light, hastens the damage to acidic papers and causes fading of fugitive pigments. Flourescent light and sunlight are much more destructive than incandescent light.

Unfortunately, regular picture glass only filters out about half of the sun's UV 
rays.  We always use ultraviolet-absorbing glass which can absorb over 97% of UV rays and are most often used by museums.