Scientists at Carnegie Mellon University have been using the Oriel Fading System to test artifacts from museum, library and archival collections.
The Oriel® Fading Test System is the result of scientists at Carnegie Mellon University developing a method for testing light - induced fading of museum artifacts, with an Oriel Light Source and Components. This testing method was then replicated by other Conservationists. Here we describe the application, which we offer as a complete system under model 80190 Fading Test System.
Light-induced fading is considered to be one of the more serious threats to artifacts. It can cause disfiguration and permanent alteration to the artifact. The 80190 Fading Test System from Newport provides rapid "screening" of the colorants present on artifacts and aids in identifying those having extreme sensitivity in the visible wavelength region.Recent field tests also indicate that the System can be used to predict color changes that would result from light exposure in particular exhibition conditions. Another useful application is to predict the longevity of a good color match for an artifact retouch. The system is particularly useful for testing the effects of exhibition lighting on newly acquired artifacts, such as archeological finds or modern art, or to test objects that will undergo changed light conditions. Most importantly, these tests are conducted without perceptible change in color to the artifact.
Most artifacts can withstand the concentrated exposure from the 80190 Fading Test System. The energy delivered typically heats a test area to ~50°C. Most objects are not likely to sustain damage as a result of this modest heating, unless they have very low-melting materials, such as in wax. This system has been used effectively to test paintings, prints and drawings, sculpture, textiles and manuscripts.
The Fading Test System delivers a concentrated pinpoint of light to a very small area of the artifact (~0.4 mm diameter), to induce fading. Simultaneously, the reflectance off the illuminated area is measured, and changes detected. Real time continuous color measurements monitor the course of fading. By comparing the fading rate of the test area to a known standard, its photosensitivity can be accurately determined. Fig. 1 shows the system components.
The system uses a 75 W Xenon arc lamp in a Series Q Housing, powered by a highly stable power source. To ensure that lamp aging and ambient temperature changes do not affect long-term light output, we include a Digital Light Intensity Controller. This control system continuously monitors the source output, compares it to a pre-set level, and adjusts the power supply to keep the measured signal at the set level. We include a Liquid Filters for Light Sources to remove the IR and two optical filters to isolate the desired 400 to 700 nm spectral region.
The filtered source output is a collimated beam; a focusing assembly is used to focus the beam onto a 200 µm diameter fused silica fiber. This fiber delivers the energy to the test area. Another focusing assembly at the output of the fiber focuses the light into a ~0.4 mm spot, on the sample surface. A second fused silica fiber, 600 µm in diameter, collects the reflectance from the illuminated test area, and delivers it to a detection system. Both fibers with focusing probes are held in a custom machined aluminum block.
The detection system is an integrated spectrometer. The detector is a photodiode array with responsivity from 375 to 900 nm. It is ideally suited for high light level measurements where small changes need to be detected. The detection system has a USB interface. Command software controls the settings; data is displayed on the computer screen and stored to disk.
The System does not include a baseplate or translation stages. Contact Newport for these or other mounting accessories.
This system is designed specifically for testing light-induced fading of museum artifacts. We can develop custom systems for other photodegradation studies. Our Solar Simulators are widely used for sunscreen and cosmetics testing and materials photodegradation studies. The large area high intensity output can simulate hours of solar radiation, in minutes. Contact us with your requirements.