What causes old maps and prints to get brown spots, and can it be fixed?

Brown spots on old paper are often called foxing. They are generally associated with factors such as humidity, impurities in the paper, mold, and poor storage, and they tend to get worse in damp conditions. Overall yellowing or browning can also come from acidic mats, backing boards, or exposure to light.

A trained paper conservator can often reduce foxing and staining with treatments suited to the specific paper and inks. Results vary, and some treatments carry risk, so this is not a job for household products like bleach, which can cause permanent damage. Ask the conservator about the likely result and how treatment might affect value.

Prevention helps most. Keep maps and prints in a stable, cool, dry environment, use acid-free mats and backing, avoid direct sunlight, and check framed pieces occasionally. If you see spots appearing, move the piece out of damp spaces and seek advice before it spreads.