Which resin type yellows as it ages, according to histology references?

• A. Natural resin
• B. Synthetic resin
• C. Both
• D. Neither

Answer: (A)

Natural resins tend to yellow as they age because their resinous compounds oxidize and form degradation products that impart a yellow-brown color. In histology, natural resins like damar or shellac-based media are known to amber with time, whereas synthetic resins such as epoxy or methacrylate embedding media are chosen for their color stability. While extreme conditions can cause some synthetic resins to yellow, the usual aging behavior is that natural resins discolor more readily. This is why references commonly note the aging yellowing of natural resins.