Vellum or parchment is a semi opaque sheet like material made from animal skin. The most commonly used animals are calf, goat and sheep.
All vellums and parchments vary in shade and markings from skin to skin and within each skin. Characteristics of the animal as a unique individual, for example age, sex, diet, stress, and state of health affect the grain pattern and visual appeal. However English Classic Calf and English Creamy White Goat vary least, while English Natural Veiny Calf and English Natural Goat vary most.