I’ve seen this done quite a number of times (especially on television Western series)–just saw Heath do it in an episode of The Big Valley. On a cattle drive, or somesuch, he took out a pencil, licked the lead tip, then wrote in a logbook.
Is this just a cliche of the genre that has no basis in reality, or did pencil lead need moistening once upon a time?
I understand that this could be a GQ, but since it involved film and TV, and seemed possibly to be utter BS, I put it here.
From what I’ve been able to find, the graphite in pencils at the time was of a lesser quality than today, and was often mixed with clay as a binder. This often made the graphite particles separate and not adhere to the paper. Licking the tip would moisten the graphite and soften it, making it leave a more readable mark.
All pencils have a combination of of clay and graphite in them. The proportions vary, which is why you get differing hardness of the graphite core - HB, 2H, 4B etc.