In a home a guzheng is an instrument. In a teaching studio it is equipment — and equipment needs an owner, a record and a replacement cycle. Studio instruments tend to fail earlier than home ones, and usually not because of quality but because nobody looked at them week by week.
What the log records. Instrument number and room, model and purchase date, date of last tuning, string changes (which string, when), humidity readings once a week, faults and repairs, and the person responsible. Paper or a shared document, either works. What matters is that somebody actually writes in it every week — a form nobody fills in is the same as no form.
Daily: thirty seconds before and after a lesson. Is the cover on, has any bridge moved, is any string visibly slack, is there a damp smell. Reset a shifted bridge to its marked position straight away rather than waiting for the next tuning: a whole lesson played with a bridge out of place teaches the student the wrong hand position and the wrong pitch.
Weekly: tune once, and look at two things while you do it. Not before every lesson, but at least once a week. While tuning, check the front nut and the string holes for fraying. Then wipe the soundboard and strings with a dry cloth — never a wet one, because water runs down the string holes.
Monthly: humidity, pins, soundboard, baseboard. Write the hygrometer reading into the log; 40–60% is the usual target band. Test the tuning pins for slip, sight along the soundboard for new cracks, and check the baseboard sound holes for distortion. In a heated northern winter or a humid southern spring, move this from monthly to weekly.
Termly and yearly: stocktake. Which instruments are due for strings — judged by hours played and tone, not by how long ago they were bought — which should be reassigned to beginners, and which should be retired. Keep exam instruments and beginner instruments managed separately: a good instrument practised on daily by beginners wears much faster.
The problem with shared use. Wear concentrates at the head end and in the middle register, where hands and picks land. Rotating instruments spreads that wear, and giving each instrument a fixed group of users is far better than having fifteen students share one. Wipe sweat off promptly; left on, it works into the finish.
What the record is really for. When something goes wrong you can see when the instrument last played normally, who used it in between and what was done — which shortens the diagnosis and makes it harder to be sold a repair you do not need. And at the next purchase round the log is the hardest evidence you have: which model lasted, which came back for repair, and which specification nobody used.
A log is not for inspections. It is a way of turning "the instrument suddenly broke" into "we knew last month it was due".