Tempered Glass/Chemical Strengthening

[bookofchange]

I recieved frightening customer service while researching Tempered Glass and Chemical Strengthening of glass.

Reached a person who had never heard of chemical strengthing, and who would not listen to my questions. I simply received canned responses, and was abruptly cut off.

How would you recommend researching local glass tempering services, and what do you know about chemically strengthened glass?

 

[alison]

Ouch. Next time you call (whether that place or any place) try asking for a technician (or if that word is too big for them, try "the person that actually does the work") That's frustrating.

 

[bookofchange]

Ouch. Next time you call (whether that place or any place) try asking for a technician (or if that word is too big for them, try "the person that actually does the work") That's frustrating.

Funny thing. I think I did get the "go to gal". I was transfered to her from the receptionist. I suspect I would have had a better experience if I had gone into the store in person. Good news though. I talked with a friend today, and he referred me to another glass place. I'm still collecting references... so personal recommendations are desired.

 

[Krish]

ROFL! I had an experience like that before dealing with ordering something. It was obvious the lady was reading (sounded like a robot) and anything that wasn't infront of her she couldn't answer I guess they do that (read) to cover their butts in the event something happens, they can say, "Well, I told you that!" Oh boy...

 

[liveforphysics]

Gotta remember, the people you get to talk to on the phone are not paid to know anything.

Chemically stengthened glass is exactly like shot-peening a metal part. All failures begin on the surface, and by applying a static and huge compression force along a very thin layer of the surface, you create an enviroment which becomes very difficult to begin a crack upon, hence the stregnthing benifits.

In shot-peening metal, the surface compression comes in the form of impacting the surface in an even fashion to a degree that the ultimate stregnth on the surface is overcome, and inelastic deformation occurs. This deformation holds pressure, causeing elastic compression on the metal just below the surface. Due to the compression, it becomes much harder to start a crack(ultimately, cracks are the cause of essentially all part failures).

Chemically strengthened glass uses the same method of operation, only carries it out in a different mannor. Since shooting thousands of tiny balls of hardened metal at the surface of glass would only end in a mess, an alternate method is required. As im sure you know, glass is SiO2, but most people dont realize that its only about 70% SiO2. The rest is Na or other things to give it special properties or colors. Na is a much smaller atom than K. By heating glass around 800-900degF in a bath of KNO3 (potash, salt-peter, stump remover), you can cause the Na to come out and play with the NO3, while the K takes its place. Now, the K is like a big fat kid sitting trying to get into an elise, 10lbs of fat kid pushing into a 5lbs kid-sack. You get surface compression, something to a tune of 100,000psi if done correctly.


Now, the overall stregnth of these parts, and the stregnth that your typical moron mechanical or civil engineer would calculate is LOWER than its stregnth prior to this procedure. This is because the internal surface compression is causeing tensile loading of its own on the core of the material. However, as usual, the civ's and ME's calculations should be disreguarded, as no formula can predict how things actually fail, which is through stress-riser points in the surface, and these processes reduce these effects by large amounts.

So, chemically treated glass, or my shot-peened engine parts both calculate out on paper to be weaker than before treatment, however, in reality they are easily around 2-10times less likely to fail VS an treated part.

The bummer in application to aquariums exists in the properties being removed from the glass for an area around 1-2" from the place it was cut. This means, unless you could get the process performed afterward the piece were cut, you wouldn't be bennifiting. I have pleanty of KNO3, and lots of high energy heating devicess, but it would require building some sort of large brick oven and other things that I'm confident my girlfriend would not appreciate in the living room, or my 2'x5' patio. Likewise, it needs to sit at the right temperature for about 8hrs to be most effective (not longer).

Perhaps a company that does powder coating could help you with this, as they allready have the ovens you would need, and KNO3 is cheap and common.

Now, tempering glass is much easier, you simply need to heat it to around 1200F, then rapidly chill it, while keeping the chilling even enough to not cause it to shatter. This essentailly puts huge internal stresses between molicules that didnt have time to arange themselves and 'chill-out'. Chips (if you are a lucky one who got a chip without causeing the whole unit to explode into corn) localize stress points in the glass, makeing failure near that area much much more likely to occur. However, it still requires some type of increase in stress to cause the failure, a continueing of a constant force which was not adquate to carpet surf your fish will not become adquate simply from time. It would require something like an earthquake, a fat kid crammed into an elise hitting it,perhaps dropping a large rock, leaning against it, or similar action.

Now, knowing where the location of the chip happens to be in relation to the design of the tank would be intigral to knowing if its a problem. Some places on aquariums are under much much more stress than others.

Hopefully this helped you, as I think I spent around an hour typing...

best wishes
-Luke

 

[wrightme43]

Good post Luke. X cycles to failure, peened or improved surface layer 3-10X cycles to failure. (Just a estimate to make a point) LOL
Things that I try to remember, almost ALL failures start at the surface. Exception in the case of inclusions but even then usually the surface. Crystals want to fix themselves. On a tank my mind tells me, every time someone walks by and the floor bounces, even a tiny bit, that is a stress cycle. Chips and cracks stop because the crystals try to repair themselves. They continue to grow when the stress is put back on them. No stress risers, no cracks, no chips, no stress cycles glass is great. Chip it, leave sharp edges, and put it on a floor that bounces. Glass in the floor. Just my thoughts, and opinions. I am not a expert at all in anything except making mistakes. LOL

 

[bookofchange]

Gotta remember, the people you get to talk to on the phone are not paid to know anything.

Chemically stengthened glass is exactly like shot-peening a metal part. All failures begin on the surface, and by applying a static and huge compression force along a very thin layer of the surface, you create an enviroment which becomes very difficult to begin a crack upon, hence the stregnthing benifits.

In shot-peening metal, the surface compression comes in the form of impacting the surface in an even fashion to a degree that the ultimate stregnth on the surface is overcome, and inelastic deformation occurs. This deformation holds pressure, causeing elastic compression on the metal just below the surface. Due to the compression, it becomes much harder to start a crack(ultimately, cracks are the cause of essentially all part failures).

Chemically strengthened glass uses the same method of operation, only carries it out in a different mannor. Since shooting thousands of tiny balls of hardened metal at the surface of glass would only end in a mess, an alternate method is required. As im sure you know, glass is SiO2, but most people dont realize that its only about 70% SiO2. The rest is Na or other things to give it special properties or colors. Na is a much smaller atom than K. By heating glass around 800-900degF in a bath of KNO3 (potash, salt-peter, stump remover), you can cause the Na to come out and play with the NO3, while the K takes its place. Now, the K is like a big fat kid sitting trying to get into an elise, 10lbs of fat kid pushing into a 5lbs kid-sack. You get surface compression, something to a tune of 100,000psi if done correctly.


Now, the overall stregnth of these parts, and the stregnth that your typical moron mechanical or civil engineer would calculate is LOWER than its stregnth prior to this procedure. This is because the internal surface compression is causeing tensile loading of its own on the core of the material. However, as usual, the civ's and ME's calculations should be disreguarded, as no formula can predict how things actually fail, which is through stress-riser points in the surface, and these processes reduce these effects by large amounts.

So, chemically treated glass, or my shot-peened engine parts both calculate out on paper to be weaker than before treatment, however, in reality they are easily around 2-10times less likely to fail VS an treated part.

The bummer in application to aquariums exists in the properties being removed from the glass for an area around 1-2" from the place it was cut. This means, unless you could get the process performed afterward the piece were cut, you wouldn't be bennifiting. I have pleanty of KNO3, and lots of high energy heating devicess, but it would require building some sort of large brick oven and other things that I'm confident my girlfriend would not appreciate in the living room, or my 2'x5' patio. Likewise, it needs to sit at the right temperature for about 8hrs to be most effective (not longer).

Perhaps a company that does powder coating could help you with this, as they allready have the ovens you would need, and KNO3 is cheap and common.

Now, tempering glass is much easier, you simply need to heat it to around 1200F, then rapidly chill it, while keeping the chilling even enough to not cause it to shatter. This essentailly puts huge internal stresses between molicules that didnt have time to arange themselves and 'chill-out'. Chips (if you are a lucky one who got a chip without causeing the whole unit to explode into corn) localize stress points in the glass, makeing failure near that area much much more likely to occur. However, it still requires some type of increase in stress to cause the failure, a continueing of a constant force which was not adquate to carpet surf your fish will not become adquate simply from time. It would require something like an earthquake, a fat kid crammed into an elise hitting it,perhaps dropping a large rock, leaning against it, or similar action.

Now, knowing where the location of the chip happens to be in relation to the design of the tank would be intigral to knowing if its a problem. Some places on aquariums are under much much more stress than others.

Hopefully this helped you, as I think I spent around an hour typing...

best wishes
-Luke

Thanks Luke! That is informative! My interest in the research was finding out if chemically strengthened glass was practical and affordable compared to heat tempered glass. It appears as though it is not. However, I have not gotten any leads on places where this is done, and how much it actually costs. The exercise was more fact finding than anything else.

BTW, do you work with glass... build tanks yourself?