Laponite residues on paper and parchment

Summary Laponite is a synthetic inorganic clay of very small particle size that disperses in water to form a thick, thixotropic, colloidal gel. It is used as a poultice in the conservation of ceramics, textiles, books and parchment to remove dirt and adhesive residues. The purpose of this study was to determine whether a residue would remain on paper and parchment substrates treated with a Laponite poultice. Samples were coated with Laponite gel that was scraped off after a fixed amount of time. Portions of the samples were also swabbed with ethanol. After accelerated ageing, samples treated with Laponite had yellowed and darkened more than untreated samples. Laponite residues were identified on all substrate types and in some instances were visible under magnification as a dried, cracked film. All analytical techniques revealed the presence of Laponite, except optical microscopy and ultraviolet fluorescence microscopy where results were inconclusive.