Paper

Papyrus had been used as a writing material in Egypt for thousands of years, and during the classical period papyrus rolls were exported throughout the ancient world. Any reader or writer, from the philosophers of ancient Greece to the emperors of Rome, would have been familiar with the papyrus roll as the normal form of the book. Typically about 12 inches tall and a hundred feet or more in length, papyrus rolls could be used to record long works of literature, or cut into smaller pieces to write letters or other short documents. [1]


Why are erasers made of rubber, and what makes them able to erase graphite?

What is happening is actually a solubility between two nonpolar solid substances, the rubber and the graphite. So the London dispersion forces (really weak intermolecular forces) between these molecules are attracted to each other and as you rub and create heat it increases the attraction and removes more graphite from the paper as it is attracted to the rubber. That's why you get dirty rubber dust.

That's also why your lead sticks to paper to begin with, those same London dispersion forces are attracting the lead to the paper. Those forces are actually a little stronger than attraction between the graphite and the rubber which is why you have to put a little energy into getting it all out.


Speaking of cost, the typical paper cup costs around two-and-a-half times the amount of a Styrofoam cup. Aside from the production of the cup, if you add the cardboard sleeve and its production, raw material, energy and shipping needs, you need to throw in an additional 2-3 cents per cup. Modifying or customizing a Styrofoam cup is nearly half the price of customizing a paper cup. The bottom line is that paper cups are more than double the price to produce and require a cardboard sleeve if you want to save your fingertips.

1   References

[1]What is a codex? https://www.lib.umich.edu/reading/Paul/codex.html