Background and current situation
Deionized water, aka Ultrapure water (UPW), is the same as water with only trace amounts of remaining dissolved salts. It is occasionally used to rinse glassware or a luxurious car to avoid shady streaks of deposits of minerals as the water dries away. A few years back, anecdotal observations suggested that UPW may have significantly better general cleaning properties than common tap-water (with some dissolved salts and minerals). Soon thereafter, it was suggested by some that UPW has such extraordinary properties that it alone, without even having to be heated, could serve as a perfectly equally efficient substitute for the traditional combination of hot tap-water and washing powder for laundry. Although this is a pretty bold claim without any clear support in the presently known chemistry of water, the mind-blowing positive effects on the environment and the reduced need of energy, made some land-lords and investors interested enough for serious business to develop. Currently this gravitates around the company Scandinavian Water Technology AB (SWATAB), which markets a combined ion-exchange de-ionizer and reverse osmosis system for the provision of UPW for laundry. A sub-group of academics within the chemistry community has been very critical and wordings such as pseudo-science and even fraud has been heard from that side, in stark contrast to several organizations that have handed out prizes to SWATAB for their bold, innovative and/or environmentally important work (see for example an early media report) SWATAB, being fully convinced of the efficacy of UPW, refers to the results of a previous independent study, which shows that UPW indeed removes stains from dirty rags to a remarkable degree, but in which study no direct comparison between UPW and tap-water has been made. Several hundreds of people are dependant on the efficacy of UPW as they now have no other means of washing their clothes in connection to their rental appartments, at least as far as the cleanness of their clothes is of concern. Further information on what has been going on around SWATAB has been collected herein elsewhere. Could it be that UPW indeed has extraordinary cleaning properties and that this fact will open up a new field of research to find out why? Could it be that UPW is better than tap-water for some things? Or, could it be that UPW is just as good as tap-water and that the latter then may be used without any de-ionizers for not-that-dirty laundry? Only a well designed, stringent and probably crowdfunded experiment will give us the clarifying answer!
The planned critical experiment
Together with primarily RISE IVF, a reputed independent test lab, an experimental set-up addressing the current questions has been discussed. The commonly used and seemingly well accepted standardized range of tests “EU Ecolobel protocol for testing laundry detergents” served as a basis for the experimental set-up. The measurables ”Stain Removal” and ”Basic Degree of Whiteness” were cherrypicked from the full range of potential tests (”Colour Maintenance” and ”Dye Transfer Inhibition” were omitted), to keep a good balance between budget and gained information and also since these measurables were used in previous similar, but less well designed, tests. Further considerations eventually led to the following experimental set-up, thus being a partial and modified version of the “EU Ecolobel protocol for testing laundry detergents”:
* Above two measurables are to be measured in three separate experiments – (i) one separate wash with deionized water alone, (ii) one separate wash with tap water with high mineral content (dH=14) alone and (iii) one separate wash with said tap water in the presence of a laundry detergent.
* The mineral content of the deionized water is to be lower than the mineral content of the corresponding deionized water of current common use in laundry.
* The laundry detergent is to be devoid of all potential bleaching agents or optical whiteners, for the isolation of any observed cleaning effect to the amphiphilic components thereof per-se.
It can be argued that a cross-comparison of the results of the above outlined experiments (i)-(iii) will prove to be a powerful argument for or against the current hypothesis “Deionized water has a cleaning effect that is significantly better than the cleaning effect of common tap water in laundry applications”. It is further believed that the results will have a high chance of providing valuable information on which direction further general development of “use of deionized water in cleaning” ought to take.
A quotation from RISE IVF on above experiment(s), and from which the target sum of this crowdfunding campaign is derived, can be found here.
UPDATE MAY 29, 2019: An alternative (minimum) protocol for comparative testing by the A.I.S.E. working group, as described in Tenside Surfactants Detergents 49(1):57-60 (Jan 2012), with the following guidelines, is also considered. [Thanks to @OlofHolmer for the tip!]