Microphones hate water, and you need to protect them from it. We’re not just talking about an obvious “don’t put your mic in the dishwasher” warning. The most common source of damaging moisture is the human voice (and, to a lesser extent, brass and woodwind instruments). Singing or speaking into a microphone subjects it to a stream of humid air and even drops of water. Even with a wind screen, some moisture can get through, and when it lands on the diaphragm it can accumulate and speed up the deterioration of the element. Over time, moisture can also cause electrical contacts to fail. When possible, use a pop filter. Pop filters are designed for a different function, but they can help shield the mic from damp air.
Although you should NEVER attempt to clean your mic’s diaphragm, there are a couple of steps you can take to reduce the harmful effects of moisture. First is to store your mics in a cool, dry place (the term “mic cabinet” isn’t just a catch phrase). Second, after a recording session, let your mics “air out’ in an open room before putting back in their boxes/pouches. Packing them up immediately means they’ll be trapped in the box with little air circulation to allow them to dry.
Clubs are particularly brutal environments for microphones. If you’re fortunate enough to play to a packed house, all those human bodies generate gallons of humidity, which mixes with that other enemy of all electronic gear, smoke. It’s best not to leave them set up overnight. Take them down and give them some time to dry in the van or at home before stowing them.