Which tool is unnecessary for removing excess ink from a pen tip?

The correct answer is identified as the ammonia solution for dilution, as it is not necessary for simply removing excess ink from a pen tip. In calligraphy and fountain pen use, excess ink can typically be handled through methods that physically absorb or wipe away the ink, such as using a cloth for blotting or tissue paper for wiping.

These methods are effective because they allow for the direct removal of ink without altering its chemical composition. On the other hand, ammonia solution, which is typically used for cleaning and can dilute or remove stains, is not a practical tool for the immediate task of managing excess ink on a pen tip, as it is more involved and could potentially damage the pen or affect the ink adversely.

Water for rinsing is also a common method for cleaning pens and removing ink, especially when more thorough cleaning is required, but it is not necessary for just absorbing excess ink in a straightforward manner. Thus, an ammonia solution is neither needed nor appropriate for this specific task.