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

The option indicating ammonia solution for dilution is correct because it is not a standard tool used for removing excess ink from a pen tip in calligraphy. Typically, tools such as a cloth for blotting, tissue paper for wiping, and water for rinsing are utilized during the ink clean-up process. These tools assist in absorbing ink, cleaning surfaces, and preventing smudging while ensuring that the writing instrument is ready for continued use. Ammonia solutions, on the other hand, are more often used for cleaning purposes in broader contexts and are not specifically required for maintaining a pen tip or dealing with excess ink in calligraphy practices. The goal in pen maintenance is to keep it clean and functional, which can effectively be achieved with the more commonly used tools mentioned.