[78-L] Cleaning VHS tapes

[Malcolm]

I know... it's not related directly to 78s but it IS related to cleaning 
audio tapes upon which 78s may recorded.
In any case I have a number of VHS tapes that have a white substance 
that has appeared not on the facing of the tape but on the top (and 
probably the bottom) of the pack. It may be related to extended storage 
without being wound/rewound. Or it could be an exudate of the tape 
itself. Or it could be a fungus or a mold or something else entirely. In 
any case, as I said, it appears most readily on the top of the tape 
pack. And not all of my tapes have been affected.
Used to be that various manufacturers offered a stand alone rewinder 
with a tape cleaner built in. IIRC there was some sort of dry pad (?) 
involved which may have slipped over one of the tape guides in the 
rewinder which would grab the gunk as the tape rewound. And there may 
have been a non-water based wet cleaner involved as well.
I'm looking for one of these beasts and striking out, even on eBay. I 
thought I might cannibalize a dead VCR and use the transport mechanism 
but the ones I had stored had motor and drive issues that affect 
winding. I just tossed 3 of them. I don't want to run any of the tapes 
through my one good, working VCR until the tape is clean enough not to 
risk damage to the machine.
So... any one have a solution?
Malcolm