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Posted by Pszemol on June 14, 2006, 5:21 pm
Please log in for more thread options > I said sometimes
I would said glass is almost always greenish...
Regardless of tempered or not.
90% of glass is greenish, even if not tempered.
So this method is totaly not feasable.
I am still waiting for Lone Gunner to tell us
what methods he knows... It might be interesting.
I have 30-gallons tank I would like to drill
and I have no idea who the tank is made by...
It has no stickers, no marks whatsoever.
It is about 10 years old with oak colored frames.
Is it Allglass? Is it Perfecto? Something else ?
No idea... I would really like to know the method
to test if the glass is tempered or not without
the need to call manufacturer and simply ask...
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Posted by Boomer on June 14, 2006, 5:56 pm
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Good luck on that. I would think that on that note then only a galss tech can
tell. And
then I wonder how good he is a telling by just tapping on.it. I think a hole
was dug and
there and he has no way out :-)
"Regardless of tempered or not.
90% of glass is greenish, even if not tempered"
Yes, I said that in my other post. The iron in the sand often gives all glass a
greenish
color. It is due to Fe++ iron. My point was, or is, is there a different hue to
the green
in say float vs tempered where one can tell the difference. That is what I
remember from
long ago and is given in the old post below. Look for tempered glass is not flat
but
rippled and viewing angle (nothing about green though)
I did a search for you on drilling tempered glass and you guessed it. I found
on guy
that has drilled tempered glass tanks 10 times, 8 out of ten tanks ended up
guess where. ?
So as far as I can, see it is a Black Art if any one can do it :-)
So Lone Gunner is way off. I want him to post one website that tells you how to
drill
temp. glass :-)
From a glass expert from one of my old aqaurium forums long ago.
"This is a response to several recent aquarium-drilling
posts.
After incrementally seeing my own ignorance in glass topics,
I spent some time with a good friend of mine with an extensive
history in the glass and optics industry. He has several patents
and has run several very large glass manufacturing companies.
If we have more questions about this stuff, I'll just invite
Alan Beatty over for another beer and we'll get the answers
right away.
Tempering glass
o Typically, the material is fed horizontally into large
furnaces that heat it to a glowing red-hot. Glass is
malleable at this point.
o Quickly remove the material from the furnace and cool
both surfaces down QUICKLY using "quenchers" (which blast
very cold air on both sides).
The result: The surface of the glass (both sides) is under
very high comression because they were cooled so quickly.
For fully tempered glass, this should be 15,000 PSI.
The internal portion of the glass cools more slowly, and is
under severe tension, being pulled to both surfaces. The
density of tempered glass and annealed (non-tempered) glass
is exactly the same: tempered is merely under compression
and tension, while annealed glass is not.
Note that this compression/tension between the surface and
the interior of the substance is the desired result of
tempering (same for glass or steel): The opposition of
force results in internal stress that makes the material
far stronger (but more brittle).
Once the glass is tempered, you can no longer work with it.
Becuase it is under severe compression (the surfaces) and
tension (the internals), it will shatter when one of the
surfaces gets a hit greater than that the surface is tempered
to handle (15,000 PSI on fully tempered glass). Thus, you
should be able to hit your aquarium pretty hard with a hammer
or baseball, but a small hit from a needle or an icepick may
shatter the whole thing (you need to exceed 15,000 PSI at
only one point). This is why a cute fuzzy little bristle
worm (marine) can shatter the side of your 29 gallon tempered
tank.
NOTE: Annealed (non-tempered) glass is typically under
no (or very low) internal pressure, closer to 400 PSI.
Thus, it won't shatter (it's not under such high tension
and compression), but it also will crack or break more
easily (it has a lower threshold: 400 PSI).
If you want to break your tempered tank, you must exceed
this 15,000 PSI limit at some point on the glass surface.
Thus, standing in a tank supported in only two corners is
fine, as long as you have 14,999 PSI (or less) stress on
those two corners (theoretically). (Ditto with the annealed
glass and the 400 PSI threshold).
RECALL: Tempered glass: 15,000 PSI must be exceeded.
Annealed glass: 400 PSI must be exceeded.
Tempered is thus better than 10 times stronger.
Automobile windshields are tempered around 10,000 PSI, and are
thus not considered "fully" tempered. When they break, you see
pieces maybe 1/4". When fully tempered glass is broken, the
pieces are very small, like 1/8" to 1/16". In fact, the temper
on automobile windshields are measured by breaking a few of
them and then counting the number and sizes of the pieces.
You can otherwise measure the temper of glass (if you don't
want to break it) by measuring a poloroid light through the
glass (tempering glass tends to polorize the glass). This
is why tempered glass often seems to have poorer visual
quality: the glass is slightly polarized, so looking at
our beautiful aquascapes at an angle may lower the viewing
quality.
You must shape the glass, put holes in it, etc. before the
tempering process. For automobiles, the glass is cut to
the desired shape (including any holes), and when it comes
out of the furnace red-hot (and malleable), it is curved.
Then, the quenchers blow cold air on it and the piece is
tempered. You can no longer cut it. Curved glass never
tempers as well as flat glass because the quenchers cannot
cool the surfaces as evenly.
Because the glass was heated to a glowing red-hot (and was
malleable), tempered glass is NEVER as straight as annealed
(non-tempered) glass. Tempered glass always has small
ripples, warps, or twists in it. Thus, there is a chance
that your aquarium won't line up as well when assembling
pieces of tempered glass. (These ripples can also
contribute to a lower viewing quality, in coordination with
the partial polarization).
However, most big tanks don't use tempered glass: While
tempered glass may be 10 times stronger than non-tempered,
the big tanks need that extra thickness for support so
nobody bothers with the tempered expense. It's better for
the little 10 gallon aquariums where the thinner, stronger
glass can save on space, shipping, and weight requirements.
Since the total stress is lower on these smaller tanks, it
is far easier for our sillicon adhesive caulk to compensate
for any un-evenness in the surfaces of the glass (it can
cover the cracks caused by tempered warping).
The tint in some glass is a result of melting the silica
with iron oxide, cobalt, selenium, or other elements to
help the glass resist alkaline etching. That's partially
why the glass is so resistant to chemical reactions even
in marine systems with a very high pH. Also, some lower
quality glass can have other photo-sensitive impurities that
may show up with time, decreasing the clarity of the glass
(recall turn-of-the-century old windows that have yellowed).
In summary, tempered glass is under severe compression at
the surface and tension internally, which allows it to shatter
when any part of its surface exceeds its temper and the
tension can "leak out". For fully tempered glass, this is
15,000 PSI. It doesn't take a lot of force for a needle
to exceed this pressure, but it takes far more for a hammer
or a baseball (with a larger surface area) to exceed this
pressure. Thus, the stories of dropping a filled 200 gallon
aquarium two feet with no breakage can be absolutely true.
Annealed glass (non-tempered glass) is in a relatively
non-stressed state (no tension or compression), which works
out to about 400 PSI surface pressure it can withstand. In
fact, many glass processing practices (cutting, drilling,
shaping) require glass to be in an annealed state (minimal
internal stress, less than 400 PSI compression). Then, you
can temper it when you are done processing it by heating it
and quenching it.
You can't ever remove the temper from tempered glass unless
you heat it to molten red-hot. (Nobody does this)."
--
--
Boomer
If You See Me Running You Better Catch-Up
Former US Army Bomb Technician (EOD)
Member; IABTI, NATEODA, WEODF, ISEE & IPS
Want to talk chemistry ? The Reef Chemistry Forum
http://www.reefcentral.com/vbulletin/index.php
Want to See More ! The Coral Realm
http://www.coralrealm.com
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Posted by Boomer on June 14, 2006, 3:42 pm
Please log in for more thread options I forgot, not necessarily. Often glass can give this color just from the iron
in the
sand, nothing else added. The color often looking down the edge of tempered
glass is often
not the same as float glass. That is why I said call to be safe
" This color is from additions they put into the glass to make it softer in
colder temps"
--
Boomer
If You See Me Running You Better Catch-Up
Former US Army Bomb Technician (EOD)
Member; IABTI, NATEODA, WEODF, ISEE & IPS
Want to talk chemistry ? The Reef Chemistry Forum
http://www.reefcentral.com/vbulletin/index.php
Want to See More ! The Coral Realm
http://www.coralrealm.com
: [..]
: > However, there is also another way, see that greenish/bluish color when you
look
: > down the edge, sometimes/usually that means it is tempered.
:
: This color is from additions they put into the glass to make it softer in
colder temps.
: Every piece of "float" glass has this greenish tint to it... tempered or not.
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