Going for the PAT
- Published: Nov 17, 2011, 7 PM
Readers may have noticed products referred to as having “passed the Photographic Activity Test” when perusing archival catalogs and wondered what this means and whether it matters for the preservation of numismatic collections.
The Photographic Activity Test was developed by the Image Permanence Institute at the Rochester Institute of Technology to test storage and exhibit materials such as labels, inks, adhesives, papers, photo albums and sleeves, and glass and framing components, to determine if they will damage photographs, slides, negatives and motion picture film.
The Photographic Activity Test is an international standard test (ISO 18916 Imaging materials — Processed imaging materials — Photographic activity test for enclosure materials). Like the Oddy Test, the Photographic Activity Test is an accelerated aging test.
The Oddy Test is named for Andrew Oddy, keeper of conservation at the British Museum, who developed this test in 1973. It is an accelerated corrosion test that determines in a short time whether a material will be corrosive over a longer period of time. It determines in advance whether a material is corrosive before it comes into contact with one’s collection.
The Oddy Test takes 28 days to complete.
Photographic Activity Test
The Photographic Activity Test uses special photographic fade and stain detectors to determine if the materials being tested will have an adverse affect on photographic material or cause staining. For the test, the materials are stacked in a sandwich with the indicators and held in a stainless steel jig. To simulate aging, the samples are placed in a special temperature and humidity chamber set at 70 degrees Celsius and 86 percent relative humidity for 15 days.
A control sample is tested at the same time. The control sample is a material known to have passed the test. The PAT is a pass/fail test. If the tested material passes, it is determined to be safe for intimate contact with photographic material. If it fails, it is not.
Although the Photographic Activity Test was not designed to test whether materials will harm coins, it is a good indicator of a material’s safety. The fade detectors will indicate if there is a possibility of the material attacking silver and less noble metals. It is important to remember that the basis of black and white photography is silver chemistry.
One should remember that commercial products can change without notice. If a manufacturer or supplier states that a product has passed the PAT, ask when the material was last tested. If the test results are a number of years old, they may not indicate the current safety of the material.
Susan L. Maltby, Toronto, is a private conservation consultant, with an interest in numismatic preservation.