Glass knife

In electron microscopy, glass knives are used to make the ultrathin sections needed for imaging.

Manufacture
Glass knives can be made in the lab quite easily. This can be done with machines designed for this purpose or a special pair of pliers. The pliers have two raised bumps on one jaw and a single bump in the direct center of the two bumps on the other jaw. The glass to be used is a 2 × 2 × 1 inch cuboid. The pliers are placed on the square's diagonal and pressure applied slowly and evenly until the piece breaks. The glass can be scored with a razor blade across the diagonal to ensure that the block breaks properly. This technique usually leaves one usable blade edge on one of the two resulting blocks. The closer the break is aligned with the diagonal, the better the cutting edge.

History
Glass knives were once the blade of choice because they could be manufactured by hand and were superior in most ways to more brittle metal blades. The advent of diamond knives quickly relegated glass knives to a second-rate status. Glass knives are still used exclusively in some labs because they are a hundred or more times less expensive than diamond knives. Mostly however, when glass knives are used, it is to cut the block down to the location of the specimen to be examined in the microscope. Then, the glass is switched out with a diamond knife for the actual ultrathin sectioning.

In Popular Culture

 * In the novel Snow Crash by Neal Stephenson, the major character Raven uses glass knives and spearheads as weapons.
 * In the computer game Morrowind (And its sequel, Oblivion), "Glass" is a class of weapon material, like "Steel", "Iron", and "Silver".