As with wfp or trad, sometimes you can hit good first time and sometimes you don't. When we went over to WFP, and what we now do with newbies is explain that sometimes windows and frames need time to adjust to this new method of cleaning, due to the amount of hidden debris in frames and surrounds etc. We explain that the majority of debris will be drawn out on the first clean, but because the purified water is still working after we have rinsed and left it may draw out more and if that is the case, please let us know and we will return to sort it out. Along the way make it sound like the customer is doing YOU a big favour by giving feedback. We had one a while ago, who in the end we had to give up on WFP usage as the seals around the glass to the frame had quater inch gaps in them and were starting
t to pull away from the glass....no amount of wfp 24/7 would make it work! The custie was good as gold and gave us feedback each time and in the end he felt embarrassed by calling us, but he was doing us a favour! We gave in and went trad on this one
In answer to the original question, there is no set rule on how many cleans it should take, as too many elements involved on different windows...But you should always aim to have good cleans on the first time, otherwise you may not get a chance to do the second and third