What is Paraffin wax?

Paraffin wax is the most widely used embedding medium for preparing histological slides. The fixed tissue not being miscible with the wax, selected pieces are passed through baths of alcohol of ever-increasing concentration in order to remove all water. The alcohol-saturated tissue is then transferred to an ante-medium which is miscible with both the alcohol and the paraffin wax. Many ante-media raise the refractive index of the tissue, imparting to it a transparent appearance. For this reason, they are commonly referred to as ‘clearing agents’, but as this is a property not possessed by all of them, the term is incorrect. The ante-medium is eventually replaced by molten paraffin wax and when sufficiently impregnated, the tissue is embedded in fresh wax which solidifies on cooling.

The paraffin wax technique permits thin individual and serial sections to be cut with ease from the majority of tissues. It also allows a multitude of staining techniques to be employed and facilitates storage of the blocks and unstained mounted sections.