Acid

Acid (in Picture Framing)

Overview

In picture framing, acid refers to materials or conditions that fall on the acidic end of the pH scale. Acidic materials can cause serious long-term damage to artwork, photographs, and documents. Paper, mat board, adhesives, and even environmental pollutants may contain acids that slowly break down fibers and lead to visible deterioration.

How Acid Affects Artwork

• Discoloration: Acids can cause yellowing or browning of paper, known as acid burn.
• Weakening of fibers: Over time, acids break down cellulose fibers, making paper or mat board brittle and fragile.
• Migrating acids: Through acid migration, acidic components in one material can transfer into neighboring artwork or mats, spreading damage.
• Outgassing: Some materials release acidic vapors, a process called acid outgassing, which can affect nearby items even without direct contact.

Sources of Acid

Acid can originate from both the materials used in framing and from environmental conditions:

• Non-archival mats and backings: Regular cardboard and wood-pulp mats are highly acidic.
• Adhesives and tapes: Many pressure-sensitive adhesives contain acids.
• Environmental factors: Pollutants, humidity, and airborne chemicals can accelerate acid-related damage.

Preventing Acid Damage

Conservation framing practices emphasize using acid-free or buffered materials to protect artwork. Some key strategies include:

• Choosing acid-free mats and backings to prevent acid burn.
• Using archival adhesives that do not degrade over time.
• Incorporating barrier layers between artwork and non-archival materials.
• Controlling environmental factors like humidity and pollutants.

Framing Industry Context

Acid control is central to professional framing. Framers and conservators educate clients on the risks of acidic materials and recommend archival solutions for valuable or sentimental pieces. The industry has shifted toward pH-neutral and buffered materials as standard practice, ensuring artwork longevity and preservation.

Related Terms

• Acid Burn
• Acid Migration
• Acid Outgassing
• Ph