Identification and care of Photographic Glass Plate negatives The Andrew W. Mellon Foundation Part 3. Preventive conservation of 19 th century Photographic Glass Plate negatives 1855: Fading committee (Poor processing, moisture, temperature and pollutants are recognized as factors) 1
Preventive Conservation Prevent means taking care of instead hands on Its better for the material Cheaper And much easier Preservation Planning for Photographic Collections Preservation Planning 1. Establish security and order 2. Assess and evaluate collection materials 3. Understand deterioration 4. Provide and maintain storage environment 5. Access and handling 6. Establish a disaster plan 2
1. Establish Security Basic security Lock on door Roof overhead Fire safety Establishing Order Purpose Physical organization Housekeeping Intellectual control 2. Assess and Evaluate Collection Materials Condition Value 3
Evaluation of Materials Identification of the different techniques Negative materials Collodion Gelatine Evaluation of Condition Collection materials exhibit: Active mold growth? Flaking binder layers? Severe image deterioration? 3. Understand Deterioration Categories of decay Mechanical Chemical Biological 4
Mechanical Decay Changes in size and shape Shrinking Swelling Deformation Stresses lead to cracks, tears Chemical Decay Oxidation of silver images (fading) Deterioration of supports Biological Decay Mold Insects 5
4. Assess and Control Storage Environment Environment causes and prevents deterioration Chemical Mechanical Biological Temperature and RH Most collections require RH between 30% - 50% Low temperature ideal max 20º C. High temp and RH provide worst possible storage conditions Normal room conditions (about 21 C/50% RH) are NOT good enough for long-term storage. 6
Monitoring Devices Devices for Environmental Monitoring Hygrothermographs Data loggers Building management systems PEM + Climate Notebook Track and analyze conditions Organizes data from PEM and other data loggers Customized analysis formats Compare view allows ranking of individual storage environments 7
Simplified Storage Guidelines Freezer NOT FOR GLASS PLATE NEGATIVES 8
Special packaging not necessary Easier to remove single items Cold Storage Vault Stabilization of Glass Plate Negatives Utilize paper envelopes or four-flap seamless enclosures (PAT required) Orient emulsion side away from central envelope seam, if present House upright in acid-free boxes (mark Glass ) Separate broken, cracked, or flaking plates (house flat) Short-term solution to this problem? 9
Proper Enclosures Buy only materials that pass the PAT (Photographic Activity Test) ISO 18916 Or use analytical filterpaper Enclosures are much lower priority than environment Design important This design is bad, can make marks in the emulsion, with high RH 5. Access and Handling Use clean and uncluttered workspace Gloves for handling unprotected materials Use extra support when needed 10
6. Establish a Disaster Plan Identify and locate most important images in collection Create emergency response team Disaster recovery Disaster Recovery Urgent attention given to: Objects with high value Water damaged materials Freezing acceptable means of stabilizing water damaged materials But not for Glass Plate negatives Timeline for camera originals 11
Gelatin Dry plates Conservation Problems: - Image silver corrosion -Separation of layers -Glass deterioration -- Mold / bacteria 1870 1839 1850 1900 1950 2000 Environmental Assessment and Control is Essential Recommended environmental conditions for photographic storage Relative humidity 30-50% Temperature 20 o C or below Low temperature and low humidity recommended for negative materials Useful ISO Standards ISO 18901. Imaging materials Processed silver-gelatin type black-and-white films -Specifications for stability. ISO 18902. Imaging materials Processed films, plates, and papers Filing enclosures and storage containers. ISO 18915. Imaging materials Methods for the evaluation of the effectiveness of chemical conversion of silver images against oxidation. ISO 18916. Imaging materials Processed imaging materials - Photographic activity test for enclosure materials. ISO 18918. Imaging materials Processed photographic plates - Storage practices. 12
END OF PREVENTIVE CONSERVATION OF 19 TH CENTURY PHOTOGRAPHIC NEGATIVES 13