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Author: Subject: Fogging Glass with NaOH?
elementcollector1
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[*] posted on 23-9-2012 at 12:46
Fogging Glass with NaOH?


Can it be done with aqueous sodium hydroxide instead of molten like NurdRage's procedure (see "Dissolving Glass with Drain Cleaner)"? I placed a test tube in a solution of very strong NaOH, but if anything it seems to be cleaning the glass. Do I need to let this sit for a few days for full effect, or what?



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Lambda-Eyde
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[*] posted on 23-9-2012 at 12:47


Make a concentrated solution and boil it for a while. That'll do the trick.



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[*] posted on 23-9-2012 at 12:48


However, molten NaOH would be so much better...



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[*] posted on 23-9-2012 at 13:01


Quote: Originally posted by Eddygp  
However, molten NaOH would be so much better...


No, it wouldn't. It's an extremely hazardous material, capable of making holes if it lands on flesh.
It would make the glass very thin and soon dissolve it completely.
He just wants it fogged, not thinned.


ellementcollector1, try boiling it in 20% lye solution. I think boiling limewater could work, too. I know it made my soda lime glass bottle foggy after a couple of years at somewhat low temperatures. Calcium hydroxide is a very strong base, almost as lye, but it's not very soluble so it's less corrosive.

Hot, dilute hydrofluoric acid works quite well, but it's very dangerous. I'd never recommend HF if less hazardous materials are available.




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[*] posted on 23-9-2012 at 13:11


HF is the best.

The original producere for making "foggy" glass is to add some NH4F to room temp cc. HF solution in a glass what is needed to be "done".

NaOH is not the best, it is corrosive as hell, if it's hot and it finds a "hotspot" at the bottom of the breaker, then it could easily make a hole in it where the lye will get out. And a hot cc. base is much worse then a hot cc. acid, believe me.




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elementcollector1
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[*] posted on 23-9-2012 at 13:14


What would I boil it in, steel? Any beaker I use would also fog.
(Also, I do need to break or melt off the end of the test tube, so if the NaOH does that for me, bonus!)




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[*] posted on 23-9-2012 at 14:08


Quote: Originally posted by elementcollector1  
What would I boil it in, steel? Any beaker I use would also fog.
(Also, I do need to break or melt off the end of the test tube, so if the NaOH does that for me, bonus!)


You could use an already damaged beaker. Never throw away half-broken glassware, you never know when it could become useful. Chipped beakers and flasks often replace vessels used for melting and intensive heating of various compounds. For example, why spending money on crucibles if you can use damaged beakers?

If you need to break off the end of a test tube, dipping it in a hot lye solution would take too much time. I'll say again - do not melt NaOH. It will almost certainly spurt and if it hits your eyeball, it's surgical eye removal for you.
As kristofvagyok said, bases are a lot worse than acids. They turn tissues to soaps.

Score one third of the tube, wet it with water and break it off using a glowing hot iron wire.
steps 1, 2, 3
Simplify things. ;)




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elementcollector1
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[*] posted on 23-9-2012 at 15:30


Don't have an already damaged beaker. All of my beakers are in relatively pristine condition (well, they need cleaning, but that's another issue).

And how would I obtain a glowing red-hot wire? My blowtorch is out of fuel, and I have no other fire sources available. Don't have a scoring tool either.
Why not wear safety glasses for the NaOH? Would it eat right through them?




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[*] posted on 24-9-2012 at 04:28


Safety glasses and proper face shields are usually made of polycarbonate plastic, they will protect your eyes from strong alkalis and acids.

Polycarbonate plastic is also very sturdy and can protect from shattering glass and metal shrapnel. Many years ago, I was wearing safety glasses while I was drilling a metal bar with a high speed drill bit, when the bit shattered and parts of it embedded deeply in a wooden 2x4 nearby, another part flew off in my direction and hit my safety glasses, making an impressive dimple in the plastic, but it did not crack.

If not for the glasses, I would have definitely lost an eye that day. Scary moment, and so glad I was wearing the safety glasses.

Robert

[Edited on 24-9-2012 by Arthur Dent]




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[*] posted on 24-9-2012 at 04:47


Quote: Originally posted by elementcollector1  
Don't have an already damaged beaker. All of my beakers are in relatively pristine condition (well, they need cleaning, but that's another issue).

And how would I obtain a glowing red-hot wire? My blowtorch is out of fuel, and I have no other fire sources available. Don't have a scoring tool either.
Why not wear safety glasses for the NaOH? Would it eat right through them?


Then use a small stainless steel pot. You can buy them in any larger store and they're not very expensive.

You don't have any other sources of fire? What kind of amateur chemist are you? :D
Just kidding. I don't know, ask a neighbour? Someone probably has a gas stove.

Of course you'd have to wear safety glasses for molten lye. If the temperature is just a bit above the melting point, a spurt on the polycarbonate would make a molten dent, but a spurt on a skin would make a hole and probably a nasty scar for the rest of your life. We're not talking about pierced first layers of skin here. You'd get a hole in your flesh and a tough to treat residual chemical burns.
But don't even think about fogging glass with molten lye. If not with injuries, you're left with a weakened glass.

Safety glasses, gloves, almost hot, 20% lye or limewater, and some time, that's all you need to fog the glass. Borosilicate glass takes more time than soda lime.

Or just buy a HF kit from an art store.

Why do you want to fog it, anyway? If you want to write on the glass, use a marker.




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elementcollector1
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[*] posted on 24-9-2012 at 05:20


I want to fog it so it reflects light differently (like, if you put LED's on both sides, the whole bar would be lit).



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[*] posted on 24-9-2012 at 06:25


Quote: Originally posted by elementcollector1  
I want to fog it so it reflects light differently (like, if you put LED's on both sides, the whole bar would be lit).
You don't need to do this chemically. You can also do it mechanically, with a sand-blaster. You don't need an industrial-sized unit; you can use one that can run off an air brush compressor. Harbor Freight sells a little unit they call an air eraser, for example. One advantage, I should point out, is that it's easier to mask with a little unit like this, because all you need is a mechanical barrier, since there's no chemical compatibility required. A friend of mine does custom-etched beer steins for his friends with the one from HF . A more lab-oriented application is to make the little etched circles and lozenges for pencil-marking flasks and beakers that seem to have been more common in the past.
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[*] posted on 24-9-2012 at 06:32


sandpaper.

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