Paper will yellow over time because of lignin in the pulped wood.
Choosing an archival, acid-free fixative means that the fixative itself should not yellow over time. Unfortunately, the primary purpose of the fixative is to prevent smudging of the media that is on your paper. While it can slow down paper yellowing over time (by reducing the surface area of ...
Charcoal is organic matter (usually wood) that has been partially burned in a low-oxygen environment. To make it, you take wood, exclude air, and apply heat.
How to make charcoal with a fire and a metal container packed full of wood pieces
small pieces of wood (eg willow or charcoal)
a metal container with a lid and vent hole(s)
an outdoor fire ...
You won't notice a lot of differences between using vine and willow charcoal.
Vine (of the grape) tends to be slightly darker in tone, is physically a little harder than willow, and I believe it has a somewhat finer structure. Vine is thinner and usually a little straighter than willow. The latter can come in a larger variety of thicknesses, which can be ...