In reply to Mike Boxall and group. This topic is in the realms of a science look up the meanings only in the Full Oxford and medical dictionaries. Pilkingtons supply pristine glass without coatings to the Double glazing industry who then clean and and make double glazed units the installers finally often but not always clean the glass with industrial petroleum/silicon compounds which coat the glass with a "wax/varnish" forever. These coatings which are also applied by householders in the form of windelene etc are the source of many of our problems they create friction squeegee drag and prevent the glass "sheeting" water, causing it to bead, concentrating liquid dirt "spots".When I was helping Peter F develop his system we spent many hours trying to solve the "problem."
There are a few DG firms that do not have any coatings and generally older glass has none.
If water sprayed or wiped on with an applicator to glass and forms droplets instead of sheeting then you have a coating. I am trying to get everyone to do away with last century polishes and embrace the new century microfibre cloths. The coating problems should be taken onboard at an international level by the Doubleglazing industry thro our own organizations.
There also appear to be two types of coatings but maybe that should go into part 2 of this topic if there is the interest.
Jeff Brimble