The Preservation Handbook Online

Table of Contents

Introduction
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

Introduction to Agents of Deterioration

Deterioration occurs to tangible materials, and damage occurs in the world of knowledge. Threats to archival and museum collections take on many forms. Variables such as geographic location, collection composition, history, storage, handling, and display will all affect the stability and rate of deterioration. Damage can result from direct physical forces, thieves, vandals, displacers, fire, water, pests, contaminants, ultra-violet light, incorrect temperature, and incorrect relative humidity. The building envelope and procedures followed during storage, display, and transit must be carefully monitored. Preventative conservation will save money and prolong the life of archival and museum collections. The following chart summarizes threats to archival collections:

Neglect
Humidity
Contaminated Air
Accident
 Excessive dryness - Embrittlement by desiccation, damage to marquetry, slackening of canvass Sulpher dioxide - bleaching tendering
Exposure to excessive light, heat and moisture Rapid fluctuation - stress to hygroscopic materials; warping of wood; flaking paint; activation of soluble salts Hydrogen sulphide - blackening of lead pigments; tarnishing of metals
Careless handling Excessive wetness - weakening of adhesives; rotting of size; mildew of leather; staining in paper; metallic corrosion; running ink; tightening of canvass; substrate changes Soot - staining
Pests - Fungi, bacteria, insects, and rodents Damp Heat - Fungi and bacteria Dust - abrasion, staining

Regular housekeeping will reduce environmental threats to the collection. Cleaning is particularly important in historical sites where the building itself is an artifact. Older architecture is less likely to be an effective barrier against fluctuations in temperature and humidity, biological invaders, and pollutants. Even the thinnest layer of dust is abravasive and scratches surfaces. Historical and contemporary cleaning practices should be researched. Many protein based materials such as wool, leather, and horsehair were used in 19th and 20th century houses. These products are a rich food source for biological invaders.

Citation

I Johnson, J. S. (1998). Soluble salts and deterioration of archeological materials. Conserve O Gram. Washington, D.C.: National Parks Service.