It is most important that any test specimens used to audit an instrument are from a traceable source and are certified by a recognised body.

Traditional methods for the evaluation of resolution in the scanning electron microscope rely upon a high-density particle upon a low-density substrate, the most popular method being evaporated gold on a carbon substrate. Although most manufacturers use this method, it is subject to abuse as there is no inbuilt magnification standard and therefore the evaluation of the image may only be made through measurement. To simply judge the specimen by appearance as most scientists do, could lead to a misleading result.

An ideal specimen for the evaluation of scanning electron microscope performance is dried polystyrene latex sputter coated with gold, or gold palladium for the evaluation of higher performance (e.g., field emission instruments) (Figure1). The specimen requires very pure polystyrene latex that is allowed to settle and dry down over a period of time sufficient for it to form a solid block. The block is fixed to a specimen stub with silver Dag and the adhesive allowed to dry.