Newspaper preservation is challenging because the paper is formulated to be inexpensive and expendable and therefore inherently unstable. It is manufactured with large percentages of unpurified wood pulp which contains impurities that remain in the paper after processing. These impurities, when exposed to light, changes in humidity and atmospheric pollutants, result in discoloration and acidic reactions to the paper. Acidity causes the paper fibers to weaken and break, and is the major reason the paper becomes brittle. Preservation of newspapers requires a stable environment: 60-70 degrees F.; 40-50% relative humidity (RH); protection from light; and storage in acid-free materials. Newspapers should be stored flat, and protected within a rigid box or folder. Added protection may be provided by interleaving the newsprint with thin sheets of buffered tissue. Never laminate or use pressure sensitive mending tape on papers you want to preserve. If papers need to be relaxed or tears repaired, seek conservation services from a qualified professional.