Low E glass cleaning

-See posts #8, 10 and 13 for some hard data on this topic, including links on manufacturer recommendations for cleaning hardcoat low-e glass.[/B]
-See post #14 for an explanation of the purpose of this thread, and how you can maybe help out
-see post #22 for info on the abraded metal issue that arrises when scraping hardcoat low e glass
-see post #23 for data on IG unit fabrication, low e coating strategies with regard to solar/thermal efficiency, as well as more data on cleaning recommendations
-see post #34 for a basic explanation of the difference between hardcoat and softcoat low e glass

here is a list of window manufacturers who’s glass we’ve cleaned in the last calendar year that make no mention of low e coating cleaning precautions (either hard coat or soft coat) on their prominent labeling (prior to first time cleaning). you can assume that it is safe to use industry-standard methods to clean windows from these manufacturers.

-weather shield

this post is for informational and research purposes only

If you’re looking for manufacturer’s recommendations for cleaning exposed hardcoat low-e coatings, you can find them on websites like pella.com.

Hardcoat low-e coatings are being used more often found on the room facing side of new residential windows, and may also be used inside IG units.
Do you know whether or not you’ve encountered an exposed hardcoat low-e coating?

You’ll never find manufacturer’s recommendations for cleaning exposed softcoat low-e coatings, because it’s only supposed to be used inside an IG unit. Any window with an exposed softcoat low-e coating is defective.
Do you know whether or not you’ve encountered an exposed softcoat low-e coating?

Gary, can you provide a link, I cannot find the information on Pella’s site and I would like to see what they are officially saying about exterior hard coat. Thanks.

Same request! Pella is starting to put Low E sticker warning labels on the exterior pane, but no indication of whether the low e side is exposed or not. Better safe than sorry


We were doing research for the AWC article on low-e, and I was having a hard time finding Pella’s instructions.
I ended up doing a site search for “SunDefense” at their pella.com site.
SunDefense is their brand name for the newer hardcoat they use - I probably could have searched for “hardcoat”.
I found their cleaning advice in the owner’s manual for wood windows, and I downloaded that, even though it was 40+ pages
Then I searched the manual for “cleaning”.
I stopped looking when I got what I needed, but if you do that same search, you might find a one page file with instructions.

In other words, it’s BS.
People, if the guy can’t or won’t say if he ever knowingly cleaned a low-e coated surface - don’t let him tell YOU how to do it.

I’ve scored some samples of softcoat low-e and hardcoat low-e glass for the hands on workshop at the Picnic.

Softcoat low-e is the most common coating inside low-e IG units. We rarely actually touch softcoat; it goes inside IG units because it’s too fragile to be exposed. We only see it if someone goofs up and assembles an IG unit wrong.
In fact, this stuff is so easily damaged, no one would sell me a sheet of softcoat low-e glass; I have to buy low-e IG units and cut them apart. Anyway - softcoat low-e glass at the workshop, so you can see for yourself what it is, and why it’s inside IG units
Hardcoat low-e - the stuff that causes problems - so you can look closely at what happens when you scrape, and if it gets marred, what you can do about that.

Additional information:

-exposed softcoat low-e will look a lot like a failed low e ig window. we’ve all seen it. the seal has failed and window looks blotchy with an irregular bronze hue. sometimes it will have a multi-hued appearance as light hits it from different directions.

-exposed softcoat looks similar to a failed low e ig unit because it’s pretty much the same phenomenon happening, just in a different location.

-instead of the distortion appearing inside the ig window due to a failed seal and exposure to outside atmosphere, the pane will usually exhibit a similar appearance on an exposed outer surface (ie., the #1 or #4 surface).

-softcoat low e can be identified, not only by it’s imperfect appearance after exposure to the elements, but also by feel. “It feels wrong, and makes your squeegee drag” when using traditional cleaning methods (ie., squeegee and solution)

-exposed softcoat low e is a manufacturer defect. to my knowledge, there is no known remedy for this defect, other than replacement. however, (full disclosure here) i don’t know everything.

You COULD simply say you have not seen it exposed - but you guess it looks like failed low-e IG units you have seen.

But I dunno if everybody’s seen whatever it is you saw; one of my customers has a failing low-e IG unit that’s several years old, and still doesn’t look anything like the nearby window that has an exposed softoat low-e.

Steve, Eric and any other readers,
Below is a collection of links to major manufacturer’s sites, where you can find their recommended cleaning methods for cleaning glass that has one or more hardcoat low-e surfaces (note- some of the manufacturers make no mention of low-e coating of any type in their cleaning instructions):

Andersen 400 series/200 series (see attached pdf, instructions on page 6)
WeatherShield (see attached pdf, pages 3-5)
Jed-Wen (see attached pdf, page 4)
Cardinal Glass (see attached pdf for cleaning instructions. this room-side {or pane #4} coated glass is advertised this way: “Its surface is smooth, making it easier to remove label residue and clean. And perhaps most importantly, there’s no haze to mar the view.”)

The above is by no means an exhaustive list. And there may be errors or something i missed. But in the interests of putting together a real resource with real help for real window cleaners, this is a start.

I noticed in my brief research that:

  • a rare few manufacturers specifically forbid the use of squeegees.
  • a few manufacturers encourage and recommend the use of squeegees
  • the vast majority of manufacturers make no mention of squeegees whatsoever (either positive or negative) in their cleaning instructions.

This leads me to this conclusion:
The cleaning methods recommended by manufacturers, for exposed hardcoat low-e coated glass or otherwise, are basically arbitrary. Those that forbid squeegee use do so as more of a liability-avoidance maneuver than an actual concern for potential negative consequences.

I think about it like this: A Q-tip box has warnings on it against sticking q-tips in your ears. but we all know what q-tips are for. Get the connection?

This conclusion is my own, and of course you’ll have to make your own decision on how strictly you follow manufacturers guidelines for cleaning hardcoat low-e (for instance, they usually recommend a solution made of vinegar and water, or Windex Multi-Surface cleaning spray…are you concerned enough to follow those instructions to the letter?)

My hope is that other window cleaners will be able to aid in the research and provide links or documentation to real printed info from manufacturers.cardinal_glass.pdf (133 KB)Cardinal_Glass.pdf (102 KB)Andersen.pdf (1.44 MB)jeld-wen.pdf (629 KB)WeatherShield.pdf (1.04 MB)cardinal_glass.pdf (133 KB)

Nice work, Caleb.

Side point: we can now put this issue to rest (hopefully). This is from Anderson’s Glossary:

“Muntin: A short bar, used to separate glass in a sash into multiple lights. Also called a windowpane divider or a grille.”

First - I feel you misrepresent the attachments by renaming them as, for instance, “Low-e glass cleaning - weathershield”
Weathershield calls that one “Use and Care” for all windows - and it does NOT mention low-e.
This seems kinda manipulative to me - if you can’t find low-e cleaning instructions for Weathershield, (or the others), you should say so.

Second - The real issue with hardcoat low-e is NOT squeegees - it’s scrapers. I don’t know why you completely IGNORE scrapers, and manufacturers’ warnings about how marks may be left on hardcoat low-e when scrapers are used.

I suppose it IS possible you’re still unaware of the scrapers versus hardcoat issue - even after you read the warning in the Pella doc, and everything that’s been said here the last week or so.
(But I’m not going to ask.)

It’s my understanding that Pella (as well as Marvin and Andersen) all use Cardinal glass - and it’s possible Pella SunDefense and Cardinal i89 are brand names for the same Cardinal room facing low-e coating.

You posted Pella’s cleaning instructions for SunDefense low-e - which actually recommend using Barkeeper’s Friend. (For metal marks from scrapers and such.)

Here are your cleaning instructions for i89 low-e - and please note how Cardinal specifically warns you not to use Barkeeper’s Friend.

This could be a problem.

some additional thoughts pertaining to post #10

-there appears to be conflicting or at least vague information amongst different manufacturers with regard to glass cleaning standards.
for instance, this manufacturer contradicts it’s own statements when it says in paragraph 1 “The coated surface of Low ‘E’ glass does not need to be cleaned differently to ordinary glass”, and yet two paragraphs later states “Wipe dry with a dry, clean lint free towel or cloth. DO NOT USE A SQUEEGEE on the Low’E’ coated (interior) surface.”

hence my conclusion that the methods manufacturers recommend are somewhat arbitrary and are designed more around avoidance of liability than anything else. it appears that manufacturers themselves are unsure of the correct and safe methods for cleaning hardcoat low-e surfaces.

so, as usual, we window cleaners will have to use a carefully balanced approach based on the printed material,our own experience, and street smarts to establish a standard method that we are comfortable with, based on what we are seeing in the field.

-all of the posted links and attachments are copied direct from the manufacturer’s sites. they are not my recommendations, they are the manufacturer’s. one common thread you will notice is that nearly all prohibit the use of scrapers. this goes for any kind of glass they produce, low-e coated or otherwise. but, you already knew that because you haven’t been living under a rock for 20 years.

-the only exception to the above that i have seen is weatherShield (see the attachment in post #10, page 3, left column half-way down) which states that new blades can be used, but scratches caused by blades will not be covered under warranty.

-if specific exposed hardcoat low-e cleaning instructions exist (for these or any other manufacturers), and you are able to locate them, please post a link in this thread or pm me and i will add them to post #10. this is an in-development resource, so we can edit the database as we get more specific and concrete information.

-all of the info collected so far is freely available on the internet. if you have no experience in a lab, or a glass factory or whatever, never fear- you can still contribute. the information regarding the manufacture of glass, either hardcoated, softcoated or non-coated is mostly available to the public at large. it requires a few minutes worth of digging (and the ability to read) but that’s about it.

my hope is that this can become a sort of crowdsourced collection of hard data, one that will be open and available to all wc’ers who need it.

I have been finding it lately on exterior side of anderson glass. During the last few years I have been finding it so easy 2 tell clients 2 get their sloppy asss contractors back 2 rectify their own laziness and neglect. I’m really not interested in accepting the responsibility from their carelessness.

What a pain in the azz…how the hell could cleaning glass become anymore difficult?

[COLOR=#b22222]You posted Pella’s cleaning instructions for SunDefense low-e[/COLOR][COLOR=#b22222] - which actually recommend using Barkeeper’s Friend. (For metal marks from scrapers and such.)
Someone on this forum, I forgot who, recommended using COPPER GLOW for metal marks. Has anyone else tried this?[/COLOR]

I don’t think these remarks really excuse you for deliberately ignoring the subject of metal marks caused by hard coatings - even the manufacturers mention metal marks.

I appreciate that you know a thing or two about glass and when you explain things to help people that’s great. But you seem to have a hard-on for Caleb. I actually haven’t seen him say one bad or negative thing about you. And he is actually trying to share what he has experienced with others here on the forum to help them. If you can add something to clarify please do. But constantly bad mouthing him doesn’t get respect from any of us. I don’t care if you are right. Cut the crap man. Enough is enough. Either say something constructive or go to sleep Gary.

Sent from my iPhone using Window Cleaning Resource mobile app

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Let me clarify this for you - Caleb refuses to share what he has experienced with low-e coatings.

Maybe he’s avoiding the subject of metal marks because it hasn’t clicked for him yet.
Or maybe he prefers to be obtuse.
I dunno.

But ignoring the issue won’t help anyone stay out of trouble over metal marks on hardcoat.

Bottom line, in a thread called low-e glass cleaning, you need to talk about the #1 low-e glass cleaning issue.