Well, until Lloyd Walker chimes in with info as to what is added to the "Step 4 rinse" (he doesn't have to give ratios or quantities), Doug's speculation in the first response would seem to me to be much more plausible and realistic than other ideas put forward here.
Think about it: it makes absolutely no sense to follow an ultrapure water rinse with anything else other than another ultrapure water or a "more" ultrapure water rinse, if you will. By adding anything to the ultrapure you would be diminishing, not enhancing, its efficacy as both a solvent and a rinse and greatly raising the possibility of leaving both a residue and a sonic signature.
I'm not saying the Step 4 is not effective, just that I doubt it is, in fact, anything more than pure or purer water than the Step 3. No one has to sell me on the merits of ultrapure-I've been using it now as the final stage of cleaning for a couple of years, usually doing 2 passes with it and I have no problem believing that more passes may improve sound quality any more than I have no problem believing a 2nd or 3rd cleaning with the right technique and fluids may well improve things with many records.
I do have a problem with what the record cleaning companies are charging for ultrapure water, but if the market will bear it, so be it.
Think about it: it makes absolutely no sense to follow an ultrapure water rinse with anything else other than another ultrapure water or a "more" ultrapure water rinse, if you will. By adding anything to the ultrapure you would be diminishing, not enhancing, its efficacy as both a solvent and a rinse and greatly raising the possibility of leaving both a residue and a sonic signature.
I'm not saying the Step 4 is not effective, just that I doubt it is, in fact, anything more than pure or purer water than the Step 3. No one has to sell me on the merits of ultrapure-I've been using it now as the final stage of cleaning for a couple of years, usually doing 2 passes with it and I have no problem believing that more passes may improve sound quality any more than I have no problem believing a 2nd or 3rd cleaning with the right technique and fluids may well improve things with many records.
I do have a problem with what the record cleaning companies are charging for ultrapure water, but if the market will bear it, so be it.