Natural resins are rarely used for mounting sections today because they are inherently what?

• A. Acidic
• B. Toxic
• C. Water soluble
• D. Non refractive

Answer: (A)

Natural resins are avoided as mounting media mainly because they are inherently acidic. The acids present in these resins can promote chemical changes in the mounted tissue over time, leading to yellowing, embrittlement, and degradation of the stain and structure. This acidity undermines long-term preservation and optical quality, which is why modern mounting media are formulated to be neutral or slightly basic and more chemically stable. Other properties—such as being water insoluble or their specific refractive index—are not the primary reason for their decline in use, though they can influence performance, they don’t override the impact of acidity.