A mixture of each binder with a barium sulphate filler (used as a white standard because of its stability) was put into a number of test tubes. These were placed on a glass stand and exposed to daylight inside a window. The aim of this type of exposure, which was relatively uncontrolled, was to simulate what would happen under normal exposure conditions (exposure in an office or a room in a home), on the understanding that any exposure in a Museum's room would improve the environmental conditions and represent a better and greater control, therefore slowing down the ageing process.
Of the mixtures produced (glass, barium sulphate and binder), only the binders are susceptible to changes (structure, chemical activity and optical properties) under the effect of light and contact with the air. Thus, the variations as determined refer exclusively to the binder. That allows us to estimate its behaviour irrespective of the other materials involved.
The eight commercial binders (references 001 to 008) were characterised using Fourier transform infrared spectroscopy on the test tubes exposed to light. Diffuse reflectance readings were taken at certain time intervals over a two-year period (from 1998 - the date of preparation - to 2000).