This process can takes minutes to weeks, depending on the tissue. Generally, 1-2 days suffice. In order for tissue to be examined with a microscope, it must be sliced into thin sections, e.g., 5-40 m m, for transillumination. In order to make thin slices, the tissue must be firmer than it is in the fresh condition. One of the most common ways to section tissue for microscopic examination is to embed it in paraffin, which allows sections to be cut without distorting tissue structure.
Infiltration requires immersing tissues in two changes of melted paraffin.
Each step should be about 0.5-1 hr long, depending on the thickness of the tissue. At this point the tissue is embedded in paraffin by placing it in a mold filled with melted paraffin. Usually a vacuum is applied to remove air bubbles. The position of the tissue in the mold is important because it will determine the orientation of the section, e.g., cross section, oblique section, or longitudinal section, etc. Fill water bath with hot water and add a pinch of gelatin.