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.
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. I use white vinegar to take out fingerprints. 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 too much of it can have an effect.
The bottom line fact is these 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, 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 but some bowls already have scratch marks from past treatment. Be careful to get any cleaning substance residues off the bowl.
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.