This has been a really excellent thread, thanks much to Flavio and ld & others!
Back in the seventies, I used the wet Lencoclean method too. And yes, the records I played wet became unplayable dry afterward. Now I have become convinced that it must been because of deposits that resulted from using Lencoclean, probably not just mineral deposits.
The Lencoclean system is still being sold by another company, but I would stay away from it as it claims to use the original Lencoclean fluid. There's now a competing product called 'Superclean' from a German company called Analogis that is apparently using superior fluid while the handling of the cleaning 'arm' and refill system seems to be much better too, according to customer reviews.
Meanwhile, I have carried out some experiments of myself as well as some outlined by ld and Flavio. For instance, I was able to use wet hygienic alcohol-based household wipes to remove loud pops from records, which were evidently due to dirt being stuck in the grooves. These pops wouldn't go away with normal washing, so I tried this. It worked, with no ill effects afterwards.
I also duplicated some of ld's experiments; again without any ill effects afterwards. Quite the reverse, actually. I would agree with DustyDave that demineralized water is a must. I used a mixture of max 20% denat 97% alcohol, demineralized water, and a few drops of washing up liquid as surfactant. I found that the quantity of washing up liquid is critical in that too much will leave deposits. I will be trying wetting agent (Photoflow or some such) later.
The vinyl-heating argument is obviously nonsense, and thoroughly busted here.
This thread also led me to think we should have a part of the VE website dedicated to "Audio Mythbusters" or maybe even a separate website called http://www.audiomythbusters.com