Search

Gas chromatography has long been used as a means of identifying proteins in acid hydrolysates of paints and adhesives on the basis of their amino acid composition. Existing procedures for amino acid derivatization can, however, take up to 4 hours per analysis, whereas a new procedure employed at the Getty Conservation Institute can be carried out in less than 20 minutes. This procedure involves the formation of N(O,S)-ethoxycarbonyl ethyl esters of amino acids using ethyl chloroformate and then a separation on an HP-INNOWAX capillary column. This procedure was employed to analyze samples from the binding media library at the Getty Conservation Institute, and amino acid compositions were tabulated for various proteins that could be used for identification purposes.

Polyester resins have been commonly used in art conservation for embedding paint cross sections prior to microscopic and analytical studies. These resins set rapidly without heat, are clear, polish readily, and microtome easily. While they work well for embedding most paint samples, they pose pro blems for some specific samples. The polyester embedding media have been found to dissolve wax, some organic colorants, and fresh natural resin layers in cross sections. The embedding resin also wicks into porous samples of low binder content. At times, infiltration can be desirable for its consolidating effects, but it can also interfere with the determination of the type of binder in the sample by producing blotchy, uneven staining results and by obstructing infrared analysis. Alternate embedding materials and procedures are discussed in this paper. One method to prevent the infiltration of embedding media is presented in which the samples are precoated with a thixotropic acrylic gel before embedding. O...