In Numismatics you are taught to always hold a coin by the rim to avoid leaving any residue on the face. With singing bowls the rim is the most important part. The way I handle singing bowls is to try to only touch the outer side, lifting them with two hands then transferring to one if I’m going to ring it in hand. Try not to grab a singing bowl with one hand, fingers inside and thumb out.
While singing bowls are made out of tough metal they also have a vulnerable side to them. Falling on to a hard surface can make cracks in brittle metal. Striking a bowl too hard, especially with an unyielding ringer can cause a sonic micro-fracture, especially thick older antiques. Cracks aren’t always fatal but often they mean the end of the sound as it was before the incident. If you suffer this misfortune, sorry, there really is no way to repair a crack that you can hear and cannot see.
Certainly you want to wipe your singing bowls out from time to time with a soft cloth to keep dust from building up. A singing bowl with caked dust in it will lose some of its sonic sparkle, and these days “dust” can include chemicals that will react with the metal. A clean cloth is best, really. If the original patina is important to you anything stronger than cloth can have an effect. On bright bowls I use white vinegar to take out fingerprints.
Singing bowls are composed of a complex mix of metals and they have been cleaned, mostly by rubbing them out with cloth or more caustic elements such as sand and mud, by their former owners. These singing bowls are tough as well as delicate and due to recent cleaning some will likely tarnish over time. If you decide to remove the tarnish, commercially available metal cleaners are just fine. If your singing bowls get really grungy somehow, start with a dry coarse woven cloth and that may do the trick. Scouring powder will scratch smoothly finished singing bowls and some bowls already have scratch marks from past treatment. Be careful to get any cleaning substance residues off the bowl.
More strenuous and harsher cleaning options are also available to you with the caveat that the sound you hear is based on the metal in the singing bowl and removing any of it can have an effect. The sound of the antique bowl that you have is a snapshot in time. Most singing bowls were originally thicker than they are now, use and cleaning over decades and centuries have removed metal. The effect of removing metal is to make the fundamental tone of the bowl deeper. The thinner the bowl gets the lower it goes. This change is in subtle degrees, however.
Sometimes rims are compromised by build-up that makes contact with a stick rough. In that case you can try steel wool, especially the new cheap Chinese imports that are not as hard as the old stainless steel ones. The tarnish and stain of many years of use is not always pleasing to people. If you want to take a bowl down to base metal anything from steel wool, copper or steel beads and chemical brass cleaners will do the trick. The base metal with its high copper and tin content will shine up wonderfully.
You can wreck a singing bowl by spraying Coke on it and letting it dry out. The metals in the singing bowl will react to the ingredients of the soda and begin a process that will deeply pit the bowl. If your singing bowls get wet, dry them promptly. I do not advise leaving water in your singing bowls for any period of time. If you play your singing bowls with water in them best to use distilled water and be sure to dry them off so you avoid water stains.
Be careful of moisture and ocean air. I may just be superstitious but I never store or transport singing bowls on their sides.
It is pretty basic but you don’t want singing bowls to rub on each other in transport and you want to protect the sides from shock. Cardboard boxes are fine but you want to protect the finish of a singing bowl, too. One of the reasons I provide cover cloths is to make this a no brainer. You’ll find it is sufficient to wrap every other singing bowl in a nest. Be careful nesting singing bowls with sides that curve in or inner lips. Leave some space as it is easier to get bowls to fit in each other than to come apart.