Describes testing of the ultraviolet-absorbent materials plastic foil and sheet to estimate their properties and suitability for use in museums. Spectra are measured before and after artificial aging in a Xenotest 450 light chamber in order to estimate the durability of the ultraviolet-absorbent compound. Also the quality and quantity of the visible light transmitted is judged. The results are to be published by the Central Research Laboratory, Amsterdam. The second example is an investigation of synthetic filling material for coins, stamps, photographs, films, and archives. Some types of plastic are of the wrong composition (e.g., polyvinyl chloride) or contain acid plasticizers (e.g., phthalate esters). The analysis of the type of plastic and additives is done by infrared spectroscopy. A short explanation of this technique is given. The use of the computer is the Fourier transform infrared instrument for the storage and retrieval of reference spectra is mentioned. A few examples are given of the material analysis of objects, e.g., a damaged anatomical model of an eyeball was supposed to consist of rubber, but it was made of a layer of thick putty-like material, containing chalk, barytes, zinc white, quartz, and shellac. A hornbook, probably of the 17th century, was analyzed to establish whether more recent materials had been used. The layer of transparent material turned out to be real horn; lacquers were asphalt and shellac. The paper page and the wood could not be tested, but the strip of lead along the edge was tested for main components and traces. On the basis of this analysis the lead was dated between 1750 and 1900. A funeral papyrus from Egypt (Thebes, XXI Dynasty) had a white powder on it. It was analyzed to determine whether it was a material hazardous to the object. It proved to be rice flour, originally used as glue. An oil painting by Van Gogh had a grayish, unsightly film covering the surface. The layer in question was sampled superficially using FTIR spectroscopy and identified as egg white. The restorer was then able to choose the appropriate solvent.