I was pottering around the Internet and found this pic. I knew playfield glass was robust but never felt the need to test it:
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Pinball info
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Playfield Glass Strength
- Thread starter Jonwolf
- Start date
you know the really expensive pinball glass that we are all buying - well there was a faulty batch...
This illustrates REALLY well the properties of tempered glass....
This illustrates REALLY well the properties of tempered glass....
I've seen that video a few times and not really got the point of it? He seems to hit it on the side, and that destroys it, but hits it in the middle with a sledge hammer, and it's OK. Is the point that 'hitting it on the side = smashed glass' is normally not a characteristic of tempered glass, so it was faulty? Ultimately 'I'm thinking, who would hit their pinball glass on the side with a hammer anyway.
So are we all supposed to test our glass with hammers?
How do you even know if it's tempered or not?
A machine I've recently bought has slightly thinner glass than any others I've had. Has a British Standard number stamped on the corner of it. Definitely not original with machine, but will i ever know if it's tempered?
How do you even know if it's tempered or not?
A machine I've recently bought has slightly thinner glass than any others I've had. Has a British Standard number stamped on the corner of it. Definitely not original with machine, but will i ever know if it's tempered?
No its not a faulty batch its all to do with shock loading over a Cross Sectional Area. the CSA on the side is minimal hence the shattering.
When glass is tempered/toughened the edges have to be chamfered (known as arrised or arrising) prior to heating this prevents the
glass from exploding in the furnace the arrising removes small cracks in the edges when the glass is cut to size.
The glass is tempered in batches and moves back and forth inside the furnace to ensure even heating and then quenched with a large
blast of air. If any of the edges touch in the furnace when moving on to the quench area the glass just explodes into the small pieces
associated with toughened glass.
All toughened glass should be laser etched to denote this no etch suspect the glass has not been toughened to British Standards. The USA tend not to etch their glass though
When glass is tempered/toughened the edges have to be chamfered (known as arrised or arrising) prior to heating this prevents the
glass from exploding in the furnace the arrising removes small cracks in the edges when the glass is cut to size.
The glass is tempered in batches and moves back and forth inside the furnace to ensure even heating and then quenched with a large
blast of air. If any of the edges touch in the furnace when moving on to the quench area the glass just explodes into the small pieces
associated with toughened glass.
All toughened glass should be laser etched to denote this no etch suspect the glass has not been toughened to British Standards. The USA tend not to etch their glass though
So in a nut shell ,take your playfield glass out side ,tap it on the edge ,and if it shatters like the V T ,all is good you had the right glass in your machine 
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Why is he constantly breaking them in the same way? Strange video????
The optical properties of the glass were at fault with the glass in the video, I think there were imperfections in the anti glare coating. As you can see there's nothing wrong with the tempering though, thats exactly how its supposed to behave. If you are actively trying to break tempered glass to get rid of it then its best to hit it on an edge.
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Or you can wrap it in old bedsheets, hitting it flat with a hammer will break it then and contain the mess, otherwise you'll end up picking up tiny sharp cubes over a large area for some time, disposed of many old fruit machines glasses this way.
You spoilt it ,I was hoping he was doing it for fun !!
