Microscopic Slides (Specimen)
There are two different types of microscope slides in general use. The common flat glass slide, and the depression or well slide. Both are rectangular and measure approximately 1 x 3 inches (25 x 75 mm). Depression slides have an indentation in the center to hold a drop of liquid, cost considerably more than the flat variety, and are usually used without a cover slip.
Standard slides are made of glass or plastic. For most purposes, glass slides of 1 to 1.2 mm thick are used. When working with high power objectives and condensers, the slide thickness should be reduced to 0.8 to 1 mm. When ordering slides, always order more than you expect to use. They usually are packaged in increments of 72 (which, incidentally, is 1/2 gross!).
A cover slip or cover glass is a very thin square piece of glass (or plastic) that is placed over the water drop. Because of surface tension, the water drop alone tends to sit in a thick dome. With a cover slip in place, the drop is flattened out allowing the investigator to focus with high power very close to the specimen. The cover glass also confines the specimen to a single plane and thereby reduces the amount of focusing necessary. Finally, the cover glass protects the objective lens from immersion into the water drop.
Glass cover slips should be handled carefully as they are very fragile and break easily. Cover slips measure 18 or 20 mm square and the glass variety is available in two thicknesses, Number 1 and Number 2. Number 1 cover glasses are 0.13 – 0.17 mm thick and are recommended for oil immersion or high resolution work. Number 2 slips are 0.17 – 0.25 thick and are used for general applications. They are sold by the ounce and there are about 120 cover slips per ounce (20 x 20 mm, Number 2). With extreme care, glass cover slips can be rinsed and reused many times.
Available in any organisms, Sell in per slide.