Many of us have experienced it – the noisy effects of silver sulfide buildup on the variable inductors of our antenna tuners.
What happens is over time a relatively high amount of silver plate on the coils reacts to form nonconductive silver sulfide.
As our tuner’s tap (usually a roller) moves across the coil it often has less than 100% conductivity and becomes noisy.
http://scifun.chem.wisc.edu/HOMEEXPTS/TARNISH.html is the simplist explaination of a method to use Aluminum Foil to draw off the sulphur and restore the silver conductive surface.
Several recent reflector postings have covered the good luck other Amateurs are having using this technique.
An alternative technique I have used is dipping in products intended for the musical instrument industry. I’ve used s Silver Dip by http://www.ferreestools.com/
In each case take care, wear your protective goggles, aprons and gloves, and be sure to rinse your inductor clean of any chemicals when finished.