How to Prepare a Wet Mount (Vaseline mount)

Living specimens do not survive long in the heat from an intense microscope illuminator bulb, usually because the specimen dries up. This problem is easily solved by preparing a vaseline chamber. Simply take a single cover slip and hold it between thumb and forefinger by the edges. Pick up some vaseline on the other forefinger and rub it over your thumb to make a film. Scrape your thumb carefully on each edge of the coverslip to make a continuous vaseline ledge.

Place a drop or two of suspension on a clean slide, and turn the coverslip over on top of the drop. Press down the edges to seal the chamber against evaporation. When preparing a vaseline mount, keep in mind that the image becomes degraded with thicker mounts, especially at high powers in dark field or phase contrast. Unless the specimen is large and fragile enough to be damaged by pressing down too hard on the coverslip, keep the chamber depth very shallow.