Photographic Activity Test
The Photographic Activity Test (PAT) is an international standard (ANSI IT9.16 and ISO18916) that tests the chemical interactions between photographs and their storage enclosures. It is meant to detect the effects of oxidation, reduction, and gelatin staining on photographs caused by their housing material.
The test was developed by the Image Permanence Institute. Materials to be tested are placed in contact with image interaction and stain detectors as seen in the diagram on the left. The stack, along with a control stack, is placed in a 70°C and 86% relative humidity chamber for 15 days to simulate aging. The image interaction (or fading) detector is composed of collodiol silver in gelatin on a polyester base. Density changes and mottling occur when in contact with harmful materials. The stain detector is unexposed and undeveloped fixed-out premium-grade black-and-white fiber-based photographic paper. Once removed from the chamber, the image interaction and stain detectors are assessed and compared to the control samples to determine if the tested material passes or fails. In order to pass the image interaction test, materials must not produce a percent image interaction difference in the collodial silver detectors greater than +/- 20% of the difference obtained with the control detector. The fail threshold for the the stain test is the density of the control stain detector +0.08 density units. If the detector shows readily visible patterns of light and dark mottling when held up to an even light source, then the material fails the PAT.
The test was developed by the Image Permanence Institute. Materials to be tested are placed in contact with image interaction and stain detectors as seen in the diagram on the left. The stack, along with a control stack, is placed in a 70°C and 86% relative humidity chamber for 15 days to simulate aging. The image interaction (or fading) detector is composed of collodiol silver in gelatin on a polyester base. Density changes and mottling occur when in contact with harmful materials. The stain detector is unexposed and undeveloped fixed-out premium-grade black-and-white fiber-based photographic paper. Once removed from the chamber, the image interaction and stain detectors are assessed and compared to the control samples to determine if the tested material passes or fails. In order to pass the image interaction test, materials must not produce a percent image interaction difference in the collodial silver detectors greater than +/- 20% of the difference obtained with the control detector. The fail threshold for the the stain test is the density of the control stain detector +0.08 density units. If the detector shows readily visible patterns of light and dark mottling when held up to an even light source, then the material fails the PAT.
In the United States, most PATs are performed by the Image Permanence Institute and are ordered by manufacturers who believe that offering materials which pass the test will lead to a higher volume of sales. When choosing enclosures for photographs, look for products which have passed the PAT.