Cleaning a Shower Head

I used a sturdy plastic bag filled with vinegar and let it sit, tightly taped, on the spout. Took something like 8 hours, but it worked. The calcium and lime deposits came right off.
If you want to do this, possibly you'd be better off trying a half hour at first. In our case, it was a "fix it or trash it" situation, so I had nothing to loose by a very long soak.

Use straight white vinegar to soak the shower head.
Then you don't have to worry about chemicals

Or, use a plastic foldover sandwich bag--not the zip type bags, put cleaner in it, and very, very carefully, put it over your shower head,(so as not to drip or spill the cleaner on you,) so the entire shower head is immersed in the cleaner, tie it, or tape it, and let it soak. Another way, is to use a wrench that will safely remove the shower head without damaging it, then put the shower head in a cleaning bowl only, and let it soak, then rinse, and using the wrench, put it back on the shower pipe.

Also, let the water run a bit, to get all of the cleaner out of the pores of the shower head--nobody wants to turn on a shower and get drenched in cleaners not meant for them.

We have the hardest water I've ever seen so far in my life, and we were hardly getting any shower flow, even though I'd clean the showerhead on the pipe. My husband got a low-flow showerhead at Walmart for around 6 dollars. Even though our water flow is still a little low, I can't believe what we are getting in water flow now. Since the other showerhead is off the pipe, I can really soak it, and check it out, and maybe with a lot of cleaning, it will be useable again! I didn't throw it out.

Use a yellow kitchen glove. Fill it with whatever you want to soak it in, and tape the ends around the shower head, and leave for a few minutes.