How many changes are recommended when processing with paraffin wax?

• A. One change
• B. Two changes
• C. Three changes
• D. Four changes

Answer: (C)

When embedding tissue in paraffin, fresh paraffin must progressively replace the clearing agent everywhere in the tissue to achieve complete infiltration. Doing three changes of molten paraffin is recommended because each change displaces more of the clearing agent and penetrates deeper into the tissue. With only one or two changes, residual solvent or incomplete wax penetration can remain, especially in larger or thicker samples, leading to poor embedding and problematic sectioning. By performing a third change, you maximize saturation of the tissue with paraffin, reduce voids, and produce a stable, well-embedded block. Maintain paraffin at the appropriate embedding temperature and allow sufficient time for each change to infiltrate thoroughly.