This post was originally written many years ago. Since that time it has received a great deal of attention. For that reason I have decided to go back again and update it. You will find pictures and a very enlightening video here. Keep coming back to this post because there will be a great deal of additional information added over time. Especially in the way of scientific/chemical knowledge and the results of some landmark experiments with a focus on visible etching of glass, deep cleaning techniques, and phobic/phylic conversion technology.
Over the years I have been personally fascinated by certain chemicals and the application of these to the practice of routine cleaning and restoration of window glass surfaces. Sodium hydroxide is not the least of these. But is one of the most interesting!
Has anyone ever worked with oven cleaner to remove staining from aluminum screens? It works really well! Sodium hydroxide has a voracious hunger for certain metals. Such as aluminum that has leached from screens. It will even eat up soda lime glass in minutes. At the right temperature and concentration.
Did you also know that restaurants use a product based on this chem to clean the grease off their grills? Did you also know that it is used at farms to completely liquify dead animals? Also it is used at 100% concentration in the form of crystals to eat up hair in household drains. Furthermore it is used in food products. It has even been used as an ingredient in certain food products. So why not clean with it?
OK. So I went out and picked up the 100% dry crystals at the hardware store. It cost me about eight bux for sixteen ounces (one pound). Here is a picture of it.
I had a pizza/sub shop to clean that I was called back into after at least four years. Use your imagination. It was bad. My cleaner was worse. It ate right through everything. There were a few windows that hadn't been touched at all for several years. They looked like they had a dark solar tint on them. So I needed to scrub a little with 0000 steel wool. But when I was done that glass was crystal clear. Of course my skin was black and dried out. Next time I will use gloves. In fact let me say this. Sodium hydroxide will really burn your skin bad. And you should never get even the smallest amount in your eyes. So gloves and goggles probably would be best. It will make pure water really hot if you put enough in a cup. When mixing it is best to use plastic cups and containers.
In practice I discovered that rather than a teaspoon per gallon I could get away with ONLY 1/8th of a teaspoon per gallon;...or less! I didn't say a tablespoon. I said a teaspoon! I use this concentration for routine cleaning at a pizza/sub shop. Not restorative deep cleaning as the one I just described. Restoration grease stripping requires higher concentrations. Remember to always used rubber gloves too. Keep your hands dry. As an interesting additional thought I was wondering about the use of super-abrasive plastic abrasives along with sodium hydroxide cleaning solutions. Also other super-abrasives.
So here are the questions. Since the technical literature that I have read indicate quite plainly that very strong alkali solutions will etch glass, will a much lighter solution of sodium hydroxide also cause etching? This video also referenced above shows how sodium hydroxide will totally eat soda lime glass under the right conditions. Much milder solutions have been used to "deep clean" glass surfaces to remove all organic molecules so that window glass becomes completely hydrophylic. I will be doing some rather interesting experiments with my "white crystals" over the next week. And will be progressively updating this post.
So here are the questions. Since the technical literature that I have read indicate quite plainly that very strong alkali solutions will etch glass, will a much lighter solution of sodium hydroxide also cause etching? This video also referenced above shows how sodium hydroxide will totally eat soda lime glass under the right conditions. Much milder solutions have been used to "deep clean" glass surfaces to remove all organic molecules so that window glass becomes completely hydrophylic. I will be doing some rather interesting experiments with my "white crystals" over the next week. And will be progressively updating this post.
We also really need to know if very mild cleaning solutions will cause the same etching effects that 1 percent solutions of hydrofluoric acid cause. To discover the answer to this question I will be performing the two different tests I have developed here for acids. It is indeed true that even water itself is quite capable of etching glass. But very slow and under conditions other than routine cleaning. So when testing cleaning/restoration solutions of sodium hydroxide we should test the concentrations used in each. Again it is obvious from the video referenced in this post if we use much higher concentrations at much higher temperatures, (such as a hot summer day) than we absolutely will etch glass.
When I tested the different acids used in so called commercial restoration products, I tested them at the concentration that was suggested they be used at. Straight out of the bottle. The MSDS gave me the name of the acid each was based on and the percent of concentration. I also tested them at the temperature they would be routinely used at. Time is also a condition. Certain acids such as hydrofluoric and sulfuric acid will show etching in as little as thirty seconds. It is even possible to create visible distortions of glass surfaces in only thirty minutes. What about when the solution puddles at the bottom of the window and remains there. This can easily happen on overcast cool days. It is also true that the glass might be dark and very hot from the sun. Both the composition of the glass and the temperature could easily contribute to the visual effects of such acids (etchants).
There are other questions that should be answered. Such as the problem of the yellowing of white vinyl window frames and vinyl siding. Oven cleaner will yellow out white vinyl in seconds. Especially on a hot day. It is based on a 4% solution of sodium hydroxide. At what concentration is a sodium hydroxide routine cleaning solution safe to use around white vinyl? To answer this I might heat up some water to about 180 degrees F. Put in a certain amount of crystals. Mix it up. Then do the dip. Dunk a strip of white vinyl used on window frames. Leave it in there for at least five minutes. Remove and inspect in bright sunlight.
When I tested the different acids used in so called commercial restoration products, I tested them at the concentration that was suggested they be used at. Straight out of the bottle. The MSDS gave me the name of the acid each was based on and the percent of concentration. I also tested them at the temperature they would be routinely used at. Time is also a condition. Certain acids such as hydrofluoric and sulfuric acid will show etching in as little as thirty seconds. It is even possible to create visible distortions of glass surfaces in only thirty minutes. What about when the solution puddles at the bottom of the window and remains there. This can easily happen on overcast cool days. It is also true that the glass might be dark and very hot from the sun. Both the composition of the glass and the temperature could easily contribute to the visual effects of such acids (etchants).
There are other questions that should be answered. Such as the problem of the yellowing of white vinyl window frames and vinyl siding. Oven cleaner will yellow out white vinyl in seconds. Especially on a hot day. It is based on a 4% solution of sodium hydroxide. At what concentration is a sodium hydroxide routine cleaning solution safe to use around white vinyl? To answer this I might heat up some water to about 180 degrees F. Put in a certain amount of crystals. Mix it up. Then do the dip. Dunk a strip of white vinyl used on window frames. Leave it in there for at least five minutes. Remove and inspect in bright sunlight.
White vinyl isn't the only other surface to look at here. There are in practice many other surfaces out there. The only way to know in advance which chemicals are safe to use around any surface would be to test your cleaning solution on that surface.
Written by Henry Grover Jr.
Written by Henry Grover Jr.
Please email me directly with any questions you might have about this article and future products I am working on or you would like to see developed.
4 comments:
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If someone stumbles here in future...
Aqueous (water) sodium hydroxide solutions do NOT etch glass at any concentration. You can store saturated sodium hydroxide solution in glass jars for DECADES without any visible damage to the glass.
It only becomes problematic at very high temperatures, at least 200C. The linked video uses _molten_ hydroxide, which requires at least 320C.
Fun fact, at this temperature even plain water will slowly damage the glass.
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