The Preservation Handbook Online

Table of Contents

I. Preservation
II. Assessment
III. Collection Assessment
IV. Agents of Deterioration
V. Monitoring collections
VI. Materials
VII. Storage
VIII. Conservation
IX. Disaster Planning
X. Housekeeping
XI. Resources / Suppliers
XII. Preservation Grants

Agents of Deterioration


Airborne pollutants are invisible enemies that attack collection materials on a microscopic level. The damage is wide spread, yet subtle, so air quality often goes neglected in many institutions. Left unfiltered, ozone with high particulate counts and corrosive gas will travel throughout the building. Small dust particles are abrasive to different surfaces and can undermine the structural stability of fragile textiles, paper and bindings. Dirt particles transport and nourish biological invaders such as mildew and mold. Corrosive gasses attack lead, tarnish silver, and act as a catalyst in metal reactions. Even rubber objects deteriorate in the presence of oxygen. "Sensitive objects may require an inert environment as well as controlled environmental conditions. This could include the use of evacuated airtight bags, oxygen scavengers and inert gases such as nitrogen."xxxv

Objects themselves can be the sources of corrosive agents. Rubber and wool release sulfur gas; PVC and PVAC can break down and release acetic and hydrochloric acid; diazo film releases ammonia; and wool and hair contain sulfur that can out gas.

Filtering air

Filtered and conditioned air is the most effective barrier to gaseous and airborne pollutants, but cost can be an inhibitive factor. When the building or storage area is climate controlled filtering can happen centrally. 3M Filterete is an electro statically charged polypropylene filter that attracts and traps large particulates such as mold spores, smoke and smog. Filtrates are expensive and must be changed every 3 months to remain effective. Fibrous filters do not protect against gaseous pollutants. "Removing gaseous pollutants requires absorbers typically consisting of beds or canisters of activated carbon or activated aluminum that is impregnated with an oxidant."xxxvi

Customized air cleaning units can be designed to suit institutional needs. Trion Air Purification Systems have several options available for commercial use. They manufacture both permanent and portable units. Permanent systems should locate air intake on the side of the building least exposed to particulate sources. The system should be designed to deliver constant treated air volume with equal disbursement through all areas of the collection. Re circulating internal air requires less cleaning by the HVAC system, however, "economizer cycles" are designed to save money by pulling in only external air. It is important that positive pressure be maintained within the building to prevent unfiltered air from entering.

Portable and "packaged" HVAC units can be used to filter particulate and condition air in limited confined parameters. Regularly serviced window units provide moderate levels of stability if left running 24 hours a day. Turning environmental control units on and off will increase fluctuation and ultimately lead to more damage.


Scavengers react chemically with corrosive gases, trapping them and removing them from an enclosure. The commercial product "MicroChamber" is available as board or sheets and is used within storage containers. The active ingredients in MicroChamber products are activated carbon and zeolites. Microchamber products protect against ozone, sulpher dioxide, oxides of nitrogen and other gaseous pollutants. Activated charcoal, silica gel, anti-tarnish cloth, and copper, zinc, silver compounds (Pacific Silvercloth) can also be used in micro-environments to control corrosive agents. Inert gasses such as Argon and Nitrogen act as oxygen scavenger and push corrosive gasses and oxygen from enclosed areas. Recently Japanese researchers at the Tokyo Metropolitan Consumer Center determined that tannin found in black and green tea leaves absorbs formaldehyde. xxxvii



XXXV. Bradley, S. M. (1990). Do objects have a finite lifetime? In S. Keeene (Ed.), Managing Conservation. United Kingdom: Institute for Conservation of Historic and Artistic Works of Art. (pp. 24-27)
XXXVI.Banks, P.N. & R. Pilette (2000). Preservation issues and planning. Chicago: ALA
XXXVII Tea bags as formaldehyde scavengers.(2000, July 22). New Updated throughout the day.
Accessed in February 2003 at, <>
XXXVIII Adapted from: Haggerman, A. E. (1998). The Tannin Handbook. Ohio: Hagerman Laboratories