Mounting media for light microscopy

To preserve a section of colored tissue for optical microscopy, it is necessary to put it on a glass slide and cover it with a thin glass slice (coverslip). The slide and coverslip must be free of optical distortion, to avoid viewing artifacts.

A mounting medium is used to adhere the coverslip to the slide and to preserve the marked sample during handling and storage.

Aqueous mounting media are available, they allow to mount the coverslip directly after the staining step. However, the solubility in water of certain dyes causes incompatibility between these dyes and aqueous mounting media (diffusion or fading of the color). In this case, it is preferable to use anhydrous or non-aqueous mounting media. It is most often solvent-based resins such as toluene or xylene. The disadvantage of using non-aqueous mounting media is that it is necessary to dewater the fabric cut prior to assembly, which adds an extra step.