calf only, while the British Standards Institution defines parchment as made from the split skin of several species, and vellum from the unsplit skin. In the usage of modern practitioners of the artistic crafts of writing, illuminating, lettering, and bookbinding, "vellum" is normally reserved for calfskin, while any other skin is called "parchment". Manufacture Vellum is a translucent material produced from the skin, often split, of a young animal. The skin is washed with water and lime (Calcium hydroxide). It is then soaked in lime for several days to soften and remove the hair. Once clear, the two sides of the skin are distinct: the side facing inside the animal and the hair side. The "inside body side" of the skin is usually the lighter and more refined of the two. The hair follicles may be visible on the outer side, together with any scarring made while the animal was alive. The membrane can also show the pattern of the animal's vein network called the "veining" of the sheet. Any remaining hair is removed ("scudding") and the skin is dried by attaching it to a frame (a "herse"). The skin is attached at points around the circumference with cords; to prevent tearing, the maker wraps the area of the skin to which the cord is to be attached around a pebble (a "pippin"). The maker then uses a crescent shaped knife, (a "lunarium" or "lunellum"), to clean off any remaining hairs. Once the skin is completely dry, it is thoroughly cleaned and processed into sheets. The number of sheets extracted from the piece of skin depends on the size of the skin and the given dimensions requested by the order. For example, the average calfskin could provide roughly three and a half medium sheets of writing material. This can be doubled when it is folded into two conjoint leaves, also known as a bifolium. Historians have found evidence of manuscripts where the scribe wrote down the medieval instructions now followed by modern membrane makers. The membrane is then rubbed with a round, flat object ("pouncing") to ensure that the ink would adhere to the surface. Even so, ink would gradually flake off of the membrane, especially if it was used in a scroll that was frequently rolled and unrolled. Manuscripts Preparing manuscripts Once the vellum is prepared, traditionally a quire is formed of a group of several sheets. Raymond Clemens