One of the more recent head cleaning cassettes. This TDK HCL-11 is from the late 1990s, and features TDK’s RC-II Rigid Construction Mechanism. All sorts of recommendations would be made by purveyors of recording devices in relation to cleaning, demagnetising or whatever, but running one of these every so often would, in my experience, keep a basic tape deck or tape recorder working without hitch. Home multi-trackers, however, needed more care, and with those, I found head cleaning tapes to have little impact when sound quality was starting to suffer.
The simple idea with these head cleaners was to make the actual tape into a suitable cleaning agent, which would rub over the heads when the cassette was run, wiping away residues which would, if not removed, dramatically dull the sound of recordings.
The actual cleaning tape in the HCL-11 was almost completely transparent, which was quite different from the cleaning tape in other brands. The advice with these was normally to run them up to around ten times. After that they were deemed ineffective or at the very least unreliable, and if you used them to serious excess they’d be more likely to degrade the sound quality than improve it.