Which of the following is NOT a criterion of a good mounting medium?

A good mounting medium plays a crucial role in preserving the structural integrity and appearance of the specimen being observed under a microscope. One of the essential criteria for such media is that it should resist bacterial and fungal growth, ensuring that the specimen remains uncontaminated over time. Additionally, a quality mounting medium should have the ability to dry quickly to a solid state, allowing for efficient preparation and observation of specimens without excessive waiting times.

Transparency and being colorless are also vital features because they ensure that the specimen can be viewed clearly without interference from the medium itself.

While maintaining a bright color after drying may seem desirable, it is not a necessary criterion for a good mounting medium. In fact, many effective mounting media are designed to be colorless to enhance the visibility of the specimen without adding any coloration that could obscure the details of the sample. Therefore, this characteristic is not fundamental to the primary purposes of a mounting medium.