Waterfed window cleaning in hot direct sunlight leaves a film

A couple of my guys insist that when cleaning windows with a water-fed pole in hot direct sunlight they have left a film or streaks over the glass even though the resin is new and they thoroughly rinsed off. Is that possible and is there a science behind it?

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What brush are the using? It’s probably just build up.

Freeway glass will have exhaust fume residue, Southwest glass will have baked on dirt. Chicago glass will have blood stains.


Possibly just blood stains then LOL.

Any other ideas?

makes no sense at all.

What happens in direct sunlight is that the glass heats up very high temperatures so you have a very high evaporation. Therefore the rinse process does not work as good so the results are not good. In the spring and fall when the sun is lower in the sky WFP in direct sunlight is very hard IMO

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I find we need to be sure that we rinse more than normal when working in direct sun especially on dark glass


Excellent advice. Thanks! Just wondering though, how would fast water evaporation cause a problem if it’s pure water?

If you have pure water and the results are spots or streaks the answer is rinse rinse rinse.


I believeissue with fast evaporation would be the dirt doesn’t get a chance to be rinsed and be flushed off the glass completely

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When you scrub the glass with your water fed brush and pure water it’s like scrubbing with a t-bar strip washer in that you have a solution dirty water across the glass . Now when you rinse the glass when the glass is very hot in direct sunlight, the rinse water (which acts like a squeegee to pull down the dirty water) dries before it can pull all the dirty solution off the glass. Answer, is rinse, rinse, rinse…then rinse again.



You can not get much more heat then in AZ . I find a hog hair nylon brush seems to take care of most of the problems . Starting a 5 am and working away from the sun does not hurt either

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Thanks for all the great advice.

I concur with the above recommendations!

Who does construction cleaning not using a ladder and only a wfp?

construction cleaning with water fed pole - YouTube More to come

It might be rinsing but it might be the brush as well. What brush are you using?

Simple nylon isn’t enough to get off build up from exhaust or baked on dirt. So it depends on what’s on the window. Boars hair does great but there are also hybrid brushes that are good too depending on how aggressive you need to be.

If all you have is nylon, you can pretreat the window with a mop - scrub the window and then rinse with nylon.

I concur with your concurrence.


Are these on vinyl windows by chance? Maybe the frames have oxidized and it wasn’t agitated or rinsed enough.

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Thanks guys - appreciate all the comments.

i came, i saw i concurred.