Scratch on glass tank leads to crack?

I was just wondering if a deep scratch on a glass tank would eventually cause the glass panel of an aquarium to crack? I'm sure the water in the tank puts a lot of pressure on the glass panel over time. What do you guys/gals think?

 

How deep of a scratch? And what size tank is it? Also, is the bottom tempered?


Glass cutting usually needs a thin scratch too to set a line for the glass to break on. If the scratch is deep enough, it could affect the strength of the glass.

 

yeah it really all depends on how deep of a scratch you're talking about.

 

I've read that a deep scratch in a panel can decrease the integrity of that panel by up to 20%. It makes a weak spot that is effected by the expansion and retraction in the glass from temp. changes. Both ambient and from the water.

 

It depends on where the scratch is, how long it is, and what side of the glass.

Worst case, it's a long deep scratch on the outside of the tank.

Glass facts! Glass has no compression limit. It can be compressed infinitely and will not fail.Eventually it will liquefy and flow, but it won't "break" under compression. It takes >1,000,000 psi to compress glass to the point of any phase change.

BUT! Glass has almost no resistance against tension. The slightest amount of force in expansion can cause breakage. The presence of a scratch or score in the glass will weaken the surface integrity of the glass and cause a breaking point to open up.

In a plate of glass, when bent the inside of the glass is put under compression, and the outer surface is under tension. In a pristine state the forces will balance for a long time before rupture, but with a scratch on the tension side you'll get an immediate break.

Since water pressure is pushing out the glass from the inside a scratch on the inside will be held close in compression and not want to break, but if it's on the outside its just the opposite and can break.


Also pressure increases with depth, so the further down the scratch is the more pressure it on it, the more likely to break.


Can you post a picture of the score?

-Doug

 

+K. Wow. I've never thought that deeply about a scratch on glass.

 

I work with glass, and I have to break it all the time... a little scratch does wonders.

Oh, and water disrupts silica bonds in glass, so a wet score is even weaker than a dry one.

I do a demo where i take a hammer, hit a sheet of tempered glass over and over and only cause a few small nicks on the surface, then take a scoring tool, score it with a hair thin score, and light finger pressure causes the entire sheet to turn into tiny little squares.... if the scoring tool doesn't do it.... glass is cool stuff.

 

The scratch is on the inside on the left panel of the tank. I can feel the scratch with my finger. It's a 72 gallon bow front tank.

 

I'd like to see that. I know what a tow chain does to the rear tempered glass of a '93 Exploder. Tiny little squares is an understatement lol. That chain popped in Dec of '04 and I still find glass everytime I vaccum.