What problem does Ninhydrin using a freon solvent virtually eliminate when processing porous materials?

Using Ninhydrin with a freon solvent addresses the issue of ink running when processing porous materials, such as paper. The traditional method of applying Ninhydrin without a solvent can lead to smudging or running of ink due to moisture, which may diffuse the ink within the porous substrate. By utilizing freon as a solvent, the application of Ninhydrin becomes more controlled, allowing for the development of latent prints without disturbing any existing ink on the surface. This results in clearer and more distinguishable prints.

The other options, though relevant to print processing, do not capture the primary issue effectively addressed by the use of a freon solvent. Smearing can occur with various methods of developing prints but is not specifically mitigated by the choice of using a freon solvent with Ninhydrin. Fading pertains more to the longevity of the developed print rather than the application process, and lint accumulation does not directly relate to the solvent choice or the process of developing prints on porous surfaces.