Which type of ink is NOT suitable for fingerprinting?

Fluorescent ink is not suitable for fingerprinting because it does not adhere well to the oils and residues that are present on a person's fingers. For an effective fingerprint, the ink needs to provide a clear and precise impression of the unique patterns on the fingertip, which fluorescent inks typically do not achieve.

In contrast, stamp pad ink is designed specifically for clear impressions and is often used for taking fingerprints. Printing ink, while potentially usable, is not as common as stamp pad ink for this specific purpose. Colored ink can be used in some situations, but it's important that it can still provide sufficient contrast for analysis. None of these options are ideal because they may not produce the fidelity necessary for the comparison and verification processes used in law enforcement and forensic contexts.