A new laser method for cleaning micropalaeontological specimens

Abstract

Abstract. A Q-Switched Nd: YAG (neodymium yttrium aluminium garnet) infrared laser can be used to clean micropalaeontological specimens, particularly those coated in gold–palladium for SEM studies. Variable pressure SEM images taken of uncoated specimens before and after laser treatment show that the laser does not have a detrimental affect on micropalaeontological specimens composed of phosphate, silica or calcite in a number of wall structural forms. The laser has no effect on the textural surface of the specimen but flakes and crinkles water-soluble mounting glues used to fix specimens to the stub. Sticky carbon tabs (Reference Agar Scientific) were found to be the best mounting medium for holding specimens in place during treatment but microfossils were prone to become detached during the process if not attached firmly. Laser cleaning has a number of advantages over traditional methods of gold removal using sodium cyanide, which is toxic, slow and does not effectively remove gold–palladium coatings due to the insolubility of palladium in the reagent. This laser removal method has potential for removing matrix from specimens as well as other types of coating and mounting media including aluminium, carbon and wax. Safe removal of coatings releases important scientific information from gold–palladium coated museum micropalaeontological specimens.