The following steps are performed after sectioning tissue samples that have been processed in a routine manner (formalin-fixed paraffin-embedded) and placing them on the glass microscopic slides:
1. Deparaffinization (usually a two-step process):
- First, the slides are placed in a drying oven to remove the water from the tissue, help adhere the section to the slide, and remove the wax around the tissue.
- Then, the slides are brought through 2–3 changes of a solvent such as xylene (a xylene substitute may also be used), which removes the remaining paraffin from the slides and tissue so that the dyes can penetrate the cells.
2. Hydration: This is accomplished by reintroducing water to the tissue using a series of graded alcohols.
- Hydration begins as the slides go through absolute alcohol, which removes the solvent/agent used for deparaffinization.
- Slides then undergo several changes of alcohols that are diluted in concentration until they reach water. This necessary process prepares the tissue to stain with the aqueous staining solution.
