Which of the following methods is NOT used to apply Ninhydrin solutions?

Brushing is not a method typically used to apply Ninhydrin solutions in latent print development. Ninhydrin is a chemical reagent commonly employed for the visualization of latent prints on porous surfaces, such as paper. The application of Ninhydrin must be done in a way that evenly distributes the solution and does not physically disturb the surface to avoid damaging potential latent prints.

Spraying, swabbing, and dipping are methods that allow for a controlled and thorough application of Ninhydrin. Spraying provides an even coat over the area being examined, while swabbing allows for targeted application with a moistened swab, ideal for small or specific areas. Dipping involves immersing the surface directly into a solution, which is effective for ensuring comprehensive coverage. Brushing, however, can lead to physical disturbance of the surface and risks smudging or damaging latent prints, making it less suitable for this chemical application.