{HEAD ~ The etching step} is preferably followed by {TAIL ~ a polishing step} which comprises providing a thin film of a second acidic aqueous etchant solution containing an alkaline earth salt; then contacting said electrode tip to the thin film: and then etching the tip at about 2 volts rms ac to thereby polish the tip 
is preferably followed by
{ HEAD ~ The etching step } is preferably followed by { TAIL ~ a polishing step } which comprises providing a thin film of a second acidic aqueous etchant solution containing an alkaline earth salt ; then contacting said electrode tip to the thin film : and then etching the tip at about 2 volts rms ac to thereby polish the tip
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH