Varmt eller kallt LED-ljus -en jämförelse av två olika ljuskällor vid Microfadetest

Abstract

In the process of exhibition design, much importance is placed on lighting. This is partly to ensure the best preservation of the objects being displayed, but also to ensure they are lit well for the visitor. Lighting policies are developed to set appropriate light levels and exposure time for the objects, while also taking the viewer's perspective into the calculation. A tool that can help to determine what light dose an object can withstand before showing colour loss is a microfade test. Microfade testing is a relatively new method which was introduced in 1999 by Paul Whitmore. Whitmore developed an instrument for accelerated light aging that can be considered non-destructive. Because the test is done on a surface that is only 0.4 mm in diameter, it can be used on even very sensitive objects. Microfade testing fills a gap where earlier methods affected the object itself. It must be possible to trust the results of an MFT test and more research is needed on the method. My study seeks to determine whether employing a cold or warm LED-light in the instrument gives the same forecast. Two light sources have been tested, one cold with a color temperature of 6200K and one warm at 4000K. The samples analysed consisted of BWS 1-3, plus five papers covering the primary colours. The samples were selected to span the entire lightfastness scale, and to be untextured and opaque. Test results showed that the cold light source gives a slightly higher value overall for color change than the warm light source for most samples. Tests on the light sensitive yellow paper displayed just the opposite results. T-tests showed that the deviation between the curves is non-relevant in all samples except for the yellow paper. On light sensitive materials however, a change in the colour of light source could provide a mis-forecast as high as one third of the light dosage. In conclusion, for most materials, the choice of lamp in the test instrument is of no significance to provide a reliable forecast of light dose. On the other hand, for light sensitive materials, it can be of great importance.