The strings of the guqin Chinese zither are either made of silk, nylon or metal-nylon.
The twisted cord of strings is then wrapped around a frame and immersed in a vat of liquid composed of a special mixture of natural glue (ingredients include Bletilla striata and isinglass) that binds the strands together.
The first is taigu 〖太古〗 [Great Antiquity] which is the standard gauge, the zhongqing 〖中清〗 [Middle Clarity] is thinner, whilst the jiazhong 〖加重〗 [Added Thickness] is thicker.
Recently in China, production of very good quality silk strings has resumed and more players are beginning to use them.
The American qin player and scholar John Thompson advocates for the use of both silk and nylon-wrapped metal strings for different styles of qin music, much like the guitar exists in both classical (nylon-string) and steel-string forms.
The nylon strings are able to be turned to standard pitch without breaking and can sustain their tuning whatever the climate unlike silk.
Many traditionalists feel that the sound of the fingers of the left hand sliding on the strings to be a distinctive feature of qin music.
The modern nylon-wrapped metal strings were very smooth in the past, but are now slightly modified in order to capture these sliding sounds.
Silk is very flexible, and can be strung to high tensions and tuned up to the standard pitch that was proposed by mainland China (5th string at A) without breaking.
Silk strings tend to be very long (more than 2 metres) and break at the point where it rubs on the bridge.
One simply ties another butterfly knot at the broken end, cut the frayed bit, then re-string.
This is good for those who lack the physical strength to pull and add tension to the strings when wrapping the ends to the goose feet.