What is a potential issue of applying paint at too high of a viscosity?

Applying paint at too high of a viscosity can lead to several problems during the painting process, with one of the most significant issues being an uneven finish. When paint is excessively thick, it may not flow properly when applied, causing it to not spread evenly across the surface. This can create areas of buildup or uneven coverage, which ultimately results in a less appealing appearance once dry. Proper viscosity is essential for ensuring the paint can smoothly level out, providing a consistent and uniform coating.

The other choices do not accurately reflect the results of using high-viscosity paint. For instance, a high viscosity does not make paint runny, nor does it typically lead to faster drying times; in fact, it often results in a longer drying time due to the increased thickness. Additionally, while a smoother finish is desirable, high viscosity tends to hinder the leveling properties of paint, making it challenging to achieve that effect.