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The Case of the Sometimes Stained Glass

A glass streaked door.
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Question about how to get rid of streaks on glass door:

Hi Glass Detective,

I have three, 8 1/2 ft tall and 1/2 in thick tempered interior doors that front a dining room wall unit. The bottom third of them are streaked. I can’t tell if it’s on the front or back. It looks like someone cleaned them but did a poor job. It does not come off. It’s only seen in certain light and with polarized sun glasses. What caused it? My housekeeper used Windex.  I tried Vinegar.  It doesn’t come off.  It’s possible that my house keeper used Clorox and water thinking it was Windex and she therefore didn’t rinse it. Could that have done it?

-Louise A.
Miami Beach, FL

Lightly visible streaks run vertically near the bottom of the glass doors

Answer to question regarding how to get rid of streaks on glass door:

Thank you for contacting Glass Detective for some help in determining what may have caused what appears to be irremovable “streaks” in your glass doors. I looked at the pictures you provided and also read your brief commentary.

Based on that review, here are my thoughts and initial response: The glass in the photos you provided is (or should be) fully tempered safety glass. That is good. Tempered glass meets most codes and is incredibly strong. The tempering of glass changes the basic structure of the glass itself by heating the glass to approximately 1200 degrees and then rapidly cooling (called quenching) the glass. This produces a piece of glass that has an outer layer of surface material that is in a “compression” state and an inner mass that is in a state of “tension.”  While this makes the glass stronger, it also changes the behavior of the glass if it should break. As such, tempered glass usually breaks into small and relatively harmless pieces of glass—although it is a mess to clean up.

Now, when you view a piece of fully tempered (heat treated), under certain lighting and shading conditions, the glass can appear to show iridescent spots or streaks and have darkish shadows. These are much more noticeable when viewed through polarizing glass lenses such as those you said you were looking through when the streaking was seen. Specifically, your e-mail states “It’s only seen in certain light and with polarized sun glasses.” If this is the case, there is nothing wrong with the glass and the streaks you have seen cannot be cleaned away … they are in the glass permanently. Typically, the thicker the glass, the more pronounced this can appear.

IF, on the other hand, you see these streak with the naked eye regardless of light conditions you may indeed have streaked and/or stained glass. Based on your description and the photos, I don’t think this is the case.

I have just a couple of more thoughts for you. First, try to find some other heavy glass tempered doors with similar lighting and put your polarized glass on and see how they look. The look will be similar, if not identical, to yours. The type of glass cleaner you use does make a difference. To this end,® will soon be making available to the consumer a glass cleaner that it has been considering to make available for some time. What formula to use and how to market it were decisions that were made only after a fair amount of testing and analysis. It should be available in about another month or so and will be competitively priced. It will be found at many locations and through Amazon®. Give it a try. I truly hope the above comments are of some help to you. And thanks again for contacting the Glass Detective.

-Glass Detective

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Lyle Hill

Lyle Hill has been in the glass and metal industry for more than 40 years. In this time he has managed glass retail, contract glazing, mirror, architectural window, window film, and automotive glass businesses throughout America. He obtained an MBA from IIT with a focus on Technology and Engineering Management. Hill is also a columnist for glass industry trade magazines and often called the “face” of the glass industry. He has also authored books including “The Broken Tomato and Other Business Parables,” which is available through Amazon. Find out more about Lyle on Linkedin.

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