Paulownia tomentosa
The sound chamber of the qin is constructed with two boards of wood, typically of differing wood types. The slightly rounded top board (soundboard) is usually made of "tong" wood 『桐』, the Chinese parasol tree, or Chinese paulownia. There are many different types of "tong" wood, the names of which are listed in the "Yuguzhai Qinpu": "wutong" 『梧桐』 ("Firmiana simplex"), "baitong" 『白桐』, "qingtong" 『青桐』 (Japanese paulownia), "paotong" 『泡桐』 ("Paulownia tomentosa"), "yitong" 『椅桐』 and "nantong" 『南桐』; the best is "wutong", but "paotong" is now widely used. The bottom board is made of "zi mu" 『梓木』 catalpa ("Catalpa ovata") or, more recently, "nan mu" 『楠木』 camphor wood ("Machilus nanmu") . The wood must be well seasoned, that is, the sap and moisture must be removed (of the top board wood). If sap remains then it will deaden the sound and, as the moisture evaporates, the wood will warp and crack. Some makers use old or ancient wood to construct qins because most of the sap and moisture has been removed naturally by time (old "shan mu" 『杉木』, "Chinese fir", Chinese Cunninghamia or Japanese Cryptomeria, is often used for creating modern qins). Some go to lengths to obtain extremely ancient wood, such as that from Han dynasty tomb structures or coffins. Although such wood is very dry, it is not necessarily the best since it may be infected with wood worm or be of inferior quality or type. Many modern qins made out of new "tong" wood (such as those made by Zeng Chengwei) can surpass the quality of antique qins. Unfortunately, the supply of good wood to make qins has dwindled in recent years, causing a rush to make more qins. Paulownia takes many years to grow and requires a curing period of at least 20 years for the sap and moisture to be properly removed. As for old wood from old houses, there are not much old houses left after modernization of the cities and towns.