Well according to my sources (my head) they say it requires silver pens.
Quote:
"'Moon-letters are rune-letters, but you cannot see them.' said Elrond, 'not when you look straight at them.
They can only be seen when the moon shines behind them, and what is more, with the most cunning sort
it must be a moon of the same shape and season as the day when they were written.
The dwarves invented them and wrote them with silver pens, as your friends could tell you.
These must have been written on a midsummer's eve in a cresent moon, a long while ago.'" |
- The Hobbit (There And Back Again, A Hobbit's Tale), A Short Rest. I couldn't tell you what page it is on though.