Bradley (1) reported a method for preparing carbon films for use as specimen substrates in electron microscopy. Since then, Bradley's technic has been improved and presently carbon films may be prepared by deposition of carbon on the surface of freshly cleaved mica. Other methods have also been developed for making carbon films, including Humphries”technic(2) and the method of Kafig(3).

The main advantage in the method presented here for the preparation of carbon films lies in its simplicity and convenience as compared to other methods. The quality of the carbon films appears to be comparable to those made by other technics.

Materials and methods. Soft glass rods approximately 4 mm in diameter were scored completely around the circumference with the scoring device shown in Fig. 1 (Mergel & Sons, San Leandro, Calif.). This instrument was developed to shear the glass rod as evenly as possible. It consists of a rubber-covered metal drum in front of which a glass rod is positioned on a stage, and against which a glass cutter, oriented perpendicular to the drum and glass rod, can be advanced. The length of glass rod to be scored is regulated by a small bent metal arm located on the righthand side of the instrument. This is attached firmly to a metal rod which can be moved laterally in the base of the device and which is secured by a wing bolt. The glass rod is scored by placing it on the stage so that one end butts against the pre-set regulating arm. The glass cutter is then driven firmly against the glass rod at a distance of 1.5 to 2 cm from the end by means of a rotating knob and screw mechanism. The rubber-covered drum is rotated so as to press the glass rod against its supporting stage, causing it to also rotate. This motion produces a deep score in the glass rod which usually causes it to fracture before it is removed from the instrument.

The small pieces of glass rod produced in this fashion were placed in suitable holes drilled in an aluminum block with the fractured surfaces up.

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Method for Carbon Film Preparation. ∗