A picture frame is a decorative surround edge, usually made of wood that is used to present and protect artworks. Together with the mount and glass, it protects artworks from environmental damage. Examples of environmental damage are acid, damp, and light. Artworks stored under normal humidity conditions, away from light, and separated by acid-free paper will retain their pristine condition for longer.
Framing to preservation standards involves the creation of an acid-free sandwich that separates the artwork from the glass and exposure to acid.
Acid is a byproduct of the breakdown of lignin. Lignin is present as a binder in all wood. All mount card made from wood potentially contains residual quantities of Lignin. Today, most mount cards have been chemically treated to remove the lignin and are pH neutral. Manufactures guarantee that the core of white-core card will keep its whiteness for 25 years. Studies have suggested that today’s PH neutral mounts should last for up to 100 years without perceivable acid damage.
The tell-tale sign of acid damage is the appearance of brown staining of paper, the bevel edge of mount card loses its whiteness and paper becoming more brittle with age. Fortunately, these are things of the past; today all mount card is PH neutral.
Museum-grade mount card
Museum-grade mount card made of cotton fibre is truly acid-free, it is more expensive but will last much longer.