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Spray-On Liquid Glass
bLanark writes with news of a new substance that can be sprayed on for a durable, easy-to-clean film on almost any substance, hard or soft. The liquid glass is essentially pure silicon dioxide, and it goes on in a layer 15 to 30 atoms thick. It is breathable and flexible, but waterproof and resistant to bacterial growth. The patent is held by a German company, Nanopool, which is in discussion with many parties about a wide range of uses: keeping public spaces sanitary, keeping restaurants clean, and keeping cars or trains clean. "The spray forms a water-resistant layer, meaning it can be cleaned using only water. Trials by food-processing companies showed that sterile surfaces covered with a film of liquid glass were equally clean after a rinse with hot water as after their usual treatment with strong bleach."
Urban legend. Glass is an amorphous solid.
Wikipedia disagrees.
In particular, the myth that glass in older houses is thicker at the bottom because it flowed definitely seems to be just that -- a myth:
Can I now avoid costly windshield replacements by simply spraying this stuff on my windshield after a ding storm, or crack?
The problem with having a crack isn't the divot where the crack started, it's the leading end of the crack. When you apply stress to a material that has a crack, the force per unit area at the tip of the crack approaches infinity, so what you have to do to keep the crack from spreading is increase its area. That's why windshield repair people drill holes at the ends of the cracks and then fill them.
Even if your intent is just to fill the much smaller divots in the glass, 30 molecules thick isn't going to make much difference. What you need is a material that has roughly the same index of refraction as the glass, that you can spread over the divots like makeup.
Nostalgia's not what it used to be.
Part of the reason for this is that water tends to act almost like a "catalyst", encouraging cracks in glass to spread much more rapidly. According to an article in Scientific American, water causes glass to crack more easily because when a water molecule enters the crack, a reaction occurs in which a silicon-oxygen bond at the crack and an oxygen-hydrogen bond in the water are cleaved, creating two hydroxyl groups attached to silicon. As a result, the length of the crack grows by the size of one bond rupture. The water reaction reduces the energy necessary to break the silicon-oxygen bonds, thus the crack grows faster.
Theoretically, any strong material that will fill the crack and prevent moisture from entering should stop the cracking process. I don't see why a film of silicon dioxide would not work as well as resin.
Actually, "play sand" is still almost entirely silicon dioxide, just like "regular sand."
The only difference is that the play sand has been washed and screened so that it has less dust and a more uniform grain size. The fact is, "toxic" silicon dioxide is all around us, and we all breathe some amount of it in every single day. Silicosis only becomes an issue for people that breathe in large amounts of it on a regular basis - i.e. people who work 40+ hours a week in fine-dust-generating industries. If the silicon dioxide found in "regular sand" was truly a health hazard, then every beach in California would be outlawed (or at least coated in warning stickers) telling you to keep away. Hasn't ever happened, and never will, since casual exposure from playing in sand is not a silicosis hazard in any way.
Another thing to consider is that given the typical chemical makeup of rocks and sand is that if it were even possible to remove all the "harmful" SiO2 from sand all you'd be left with was a fine dust of metals and trace elements which would be harmful if played in.