BRASS KEYS etc.
The keys and other metal parts of some recorders are made of untreated brass. Over a period of time they will develop a dull patina, or tarnish, which may include fingerprints.
To reduce this effect store the instrument in its case and keep any cleaning mop or swab out of the case. Do not handle the metal parts needlessly and wipe over the metal work with a clean duster or similar after each playing session. If at all possible, avoid touching the metal with sweaty hands.
The sparing application of a wax polish to the brass parts will slow the tarnishing process.
Mild discolouration may be removed with a "silver cloth". Heavy discolouration may be removed with a car body colour restorer, "T-Cut", or similar. Finish off with a silver cloth followed by a clean cloth. Be miserly with the cleaning medium. Avoid the wood. This is a dirty job!
The brass sleeve on the new Moeck renaissance instruments should be wiped clean after each session. When the cork joints associated with the sleeve are greased the cork will pickup a black stain from the brass. This is unavoidable, but of no consequence.
Handle mouth pipes close to the point of entry into the recorder, they will not stand "yanking" and kink very easily.