Microscope slides are used to view specimens through a compound microscope. They come in different sizes and styles, including plain, concave, and well slides. Wet mounts are used for live or liquid specimens, while permanent slides are for dead specimens. Crosslinked and mica slides also exist.
Microscope slides are used to view samples through a compound microscope. This type of microscopy is illuminated by light and produces a high-magnification, low-resolution image. Specimens can be alive or dead and are mounted on glass or plastic microscope slides. These slides come in different sizes and styles depending on the purpose and object being displayed. Standard slides range in thickness from one millimeter (1 mm) to one and two tenths of a millimeter (1.2 mm), but thinner slides are used with high-powered microscopes.
Microscope slides can be plain and flat, or they can be concave, with a well or depression in the slide to hold a drop of liquid. Well slides are more expensive than plain slides and are usually used without a coverslip. Coverslips, also called cover slips, come in two standard thicknesses, number one and number two. Slides number one are for higher resolution microscopy and have a thickness of 0.13mm to 0.17mm, while slides number two are for more general use with a thickness of 0.17mm to 0.25mm. Cover glasses are used to keep the microscope lens from touching the specimen and to flatten and homogenize the water in a wet mount.
A wet mount is a common preparation of microscope slides used to view liquid specimens, live specimens, or any type of specimen that needs to be kept moist. To prepare a wet mount, the sample and a drop of water are placed on a flat side using a pipette or medicine dropper. The coverslip is then carefully placed at an angle over the flat slide so that the water is evenly distributed between the two slides. It’s important to use the right amount of water, because too little can crush the sample or leave it drying too quickly. Too much water can cause the coverslip to slip and allow live specimens to swim too freely, making focusing difficult.
Permanent microscope slides, unlike wet mount slides, can be prepared well before the slide is used and will include only dead specimens. A permanent slide locks a sample into a resin seal created by the evaporation of a solvent. There are several types of permanent microscope slides referred to by different abbreviations. “wm” stands for the whole frame or a whole sample, “ls” is for longitudinal section, “cs” is a cross section, “sq” is a squash preparation of the sample, “sm” is for smear and “st” it is a stained specimen. Colored organisms can be alive or dead, are often easier to see, and are used in freshly made slides as well as permanent slides.
In addition to the normal flat microscope slides and well slides, there are also crosslinked slides. This special purpose slide has a grid printed on it so that the observer can estimate the size of the sample under observation. While no longer in common use, clear mica slides also exist, as originally employed in the Victorian era. Today, mica is sometimes used when glass microscope slides are too dusty, scratched, or cause too much glare.
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