The glossary continues: “Nitrate film and highly acidic paper suffer inherent vice because they are chemically unstable. An object made of metal and leather suffers inherent vice because the leather causes the metal to corrode.”
One example of inherent vice you have all seen in your family papers are the yellowing and brittleness of newspaper clippings. This is due in part to chemicals that are added to newsprint (highly acidic paper) to speed its production. Those chemicals (the inherent vice) in turn cause deterioration.
You may also have noticed nineteenth-century letters, diaries, or other written documents in which the ink has stained the surrounding paper and, in severe cases, eaten through the paper itself.
This would be an excellent example of inherent vice in action. Iron gall ink was the standard writing ink from the 12th through the 20th century, made from varied formulas that included iron salts, tannin (galls), gum Arabic, and water. The high iron content in the ink (the inherent vice) stains and eventually corrodes the underlying paper.
Only a trained professional conservator can help documents with iron gall ink damage. But you can make sure that these documents in your collections are stored in cool, dry locations and use buffered acid-free interleaving paper to keep those pages separate from other documents.