Resinous mounting media are usually dissolved in toluene, xylene, or xylene substitutes.

• A. True
• B. False
• C. In ethanol
• D. In water

Answer: (A)

Resinous mounting media are hydrophobic and require nonpolar organic solvents to dissolve them. Toluene, xylene, and xylene substitutes are the solvents that effectively dissolve these resins so they can be applied as a mounting medium and form a clear, durable film once the solvent evaporates. Water and ethanol are polar solvents that do not dissolve resinous mounting media, leading to poor dissolution, cloudiness, and poor adhesion. In practice, using these organic solvents ensures the resin mixes uniformly with the mounting medium and produces a stable, transparent cover slip.