Why not blot dry the negative stain?

Blotting dry the negative stain can cause the stain to become uneven or streaky, leading to inaccurate results when viewing the sample under a microscope. Negative stains are typically left to air dry in order to evenly coat the sample and provide a clear background for observing the cells or structures being stained. Blotting dry may disrupt this even coating and affect the quality of the staining.

A negative stain is used to visualize negatively charged structures in a sample. The stain is applied to the sample and then washed away, leaving only the negatively charged structures stained. If the negative stain is blotted dry, the stain will be removed from the negatively charged structures, making them difficult to see.