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#1
Old 03-22-2011, 07:52 PM
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Glass with embedded wire mesh...purpose?

I haven't been around a modern classroom recently, but I remember in my own elementary school all of the windows were made of that kind of glass that has little wires criss-crossing making diamond shapes.

I always wondered what was the point of that wire mesh.

Security?
If someone smashes in the window, then they have to deal with the thin chicken wire as well. But that would only slow them down. Couldn't they just clip the wires? A stout hunting or diver's knife would probably make short work of the wires.

Safety?
Sure, it might hold the glass together (and save a kid, perhaps), but why not just use the same plastic sandwich that is used for automobile windshields? It would be transparent and probably even safer.

So what's it all about?
#2
Old 03-22-2011, 07:59 PM
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Quote:
Originally Posted by minor7flat5 View Post
I haven't been around a modern classroom recently, but I remember in my own elementary school all of the windows were made of that kind of glass that has little wires criss-crossing making diamond shapes.

I always wondered what was the point of that wire mesh.

Safety?
Sure, it might hold the glass together (and save a kid, perhaps), but why not just use the same plastic sandwich that is used for automobile windshields? It would be transparent and probably even safer.
Yes, safety. It is to prevent large shards of glass from getting all over the place.

Laminated glass could achieve the same effect. I don't believe it was popular even for cars until around 1940, and the wire mesh glass was less expensive. It is also easier to visually confirm that the glass is a safety type and not some random pane. It is also easier to cut to size than either laminated glass or tempered glass (which must be cut before tempering).
#3
Old 03-22-2011, 08:02 PM
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Googled "wire mesh glass".

From the second search result:

Quote:
It is manufactured primarily as a fire retardant, with wire mesh inlaid in the glass to prevent it from shattering and breaking out under stress or when exposed to high temperatures.
Quote:
...the wire in the glass actually weakens the glass from a strength standpoint, and makes it more susceptible to breaking. What the wire does do for the glass is hold it in place. That makes it safer from the standpoint that a broken window won't send glass fragments showering through a room (hence its use in schools), and that the wire will hold the glass in place under extreme temperatures (hence its status as fire rated glass).
#4
Old 03-22-2011, 08:15 PM
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So it's not to make middle school feel like even more of a prison?
#5
Old 03-22-2011, 08:40 PM
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I am not sure about that wire mesh, but flames wouldn't penetrate the screen door looking stuff used in laboratory. I shudder when I remember organic chemistry lab in the 60's with 20 of us boiling benzene over an open flame in an open room.
#6
Old 03-23-2011, 04:42 AM
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Originally Posted by thelabdude View Post
I am not sure about that wire mesh, but flames wouldn't penetrate the screen door looking stuff used in laboratory. I shudder when I remember organic chemistry lab in the 60's with 20 of us boiling benzene over an open flame in an open room.
That's the same effect exploited by Humphrey Davy for his famous safety lamp, however, I'm sure flames would penetrate a grid of thin wire with 1cm holes in it.
#7
Old 03-23-2011, 06:43 AM
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Quote:
Originally Posted by Terry Kennedy View Post
Yes, safety. It is to prevent large shards of glass from getting all over the place.

Laminated glass could achieve the same effect. I don't believe it was popular even for cars until around 1940, and the wire mesh glass was less expensive. It is also easier to visually confirm that the glass is a safety type and not some random pane. It is also easier to cut to size than either laminated glass or tempered glass (which must be cut before tempering).
Bolding mine.

I would have never thought of that, but it is a quite valid point.

Quote:
Originally Posted by Pasta View Post
Googled "wire mesh glass".

From the second search result:
Thanks! It's a little embarrassing that an answer was in the second result.
I was also looking for the kind of stuff like was posted above—there's enough folks here in fire safety related work who can provide insight that a vendor page might not provide.

Do you have any personal knowledge of this subject?
#8
Old 03-23-2011, 07:05 AM
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Quote:
Originally Posted by asterion View Post
So it's not to make middle school feel like even more of a prison?
That's just a side benefit.
#9
Old 03-25-2011, 02:02 PM
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I once saw someone push the glass on the door instead of the door itself, his hand went through the glass and the wire. That's gotta make the injury worse.
#10
Old 03-25-2011, 02:27 PM
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Code requires it in places like stairwell entrance doors, because of the fire rating of the space. It gives a bit of extra time for residents to evacuate. Most new buildings just use solid fire-rated doors.

Last edited by Chefguy; 03-25-2011 at 02:28 PM.
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