Cello inexpensive wood that has been blackened or "ebonized" to look like ebony, which is much harder and more expensive. Ebonised parts such as tuning pegs may crack or split, and the black surface of the fingerboard will eventually wear down to reveal the lighter wood underneath. Historically, cello strings had cores made out of catgut, which, despite its name is made from sheep or goat intestines which are dried out. Most modern strings used in the 2010s are wound with metallic materials like aluminum, titanium and chromium. Cellists may mix different types of strings on their instruments. The pitches of
Catgut infection. Catgut sutures remain in use in developing countries where they are locally less expensive and easier to obtain. Catgut treated with chromium salts, known as chromic catgut, is also used in surgery. Natural gut is still used as a high-performance string in tennis racquets, although it had more popularity in the past and is being displaced by synthetic strings. To prepare catgut, workers clean the small intestines, free them from any fat, and steep them in water. Then they scrape off the external membrane with a blunt knife, and steep the intestines again for some time in potassium hydroxide.