Good Evening,
Sharpies are great, as others have indicated above.
Even Sharpies, however, don't work very well for writing information on negatives--IF you want the written material to be easily readable on a contact sheet. The Sharpie ink, even the black ink, is apparently not quite opaque; I find that india ink is much more satisfactory for marking negatives. In addition, even the finest-point Sharpies are too blunt to use effectively on the limited clear space of 4 x 5 negatives, especially, again, if you want the any data to be clear on the contact sheet. Otherwise, Sharpies are terrific.
Konical