Can I use calligraphy ink in my fountain pen?

No, it is not recommended to use calligraphy ink in a fountain pen. Calligraphy inks are typically designed for dip pens or specialized calligraphy brushes, meaning they are usually thicker and contain more particulate matter such as pigment or gum arabic. These characteristics can lead to clogs and other performance issues in a fountain pen, whose feed channels are engineered for the thinner, more fluid consistency of fountain pen inks. To ensure optimal writing performance and avoid damaging your pen, always use inks that are specifically formulated for fountain pen use.