I’m a big old animal lover, so I won’t go too deep into the details of how parchment is made. It’s roughly the same process as making leather, with lots of soaking and stretching and scraping. You soak an animal skin in water, then water and lime (to get the fur off), for a week or two; stretch it on a frame; scrape it smooth with a knife; and dry it.
The result is a smooth, thin, durable (it lasts for centuries) material that is a treat to write on. Vellum is just thick enough that if you make a goof, you can scrape off the dried ink with a sharp blade and write over it (look at mediæval pictures of scribes at work—they hold both a pen and a small knife). If you want to make your own parchment, Lisa Parris gives you the recipe here. ourpastimes.com/make-vellum-4814566.html As Western Civ Irregular and animal-lover Heidi K points out, it’s worth noting that parchment makers were being respectful of the animal by using every bit of it.
If you like cute baby calves and live in the country (in northeastern USA), maybe you’d like to foster this adorable guy. He’s not available for making parchment out of! https://www.facebook.com/SperanzaAnimalRescue/photos/pcb.3693007027481424/3693006924148101/
Here’s where to buy ethically-sourced vellum:
Skip ahead to 5:30 to see this guy writing on parchment—
Back to the beginning of The Western Civ User’s Guide to Reading & Writing.