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Glass Tanks

Contents:

  1. glass vs plexiglass
    by marat-at-ccu.umanitoba.ca () (Thu, 13 Aug 1992)
  2. tank rack].
    by howardr-at-col.hp.com (Howard Rebel) (16 Feb 1994)
  3. tank fabrication
    by dbailey-at-bcarh673.bnr.ca (Douglas Bailey) (Wed, 7 Apr 1993)
  4. Need Advice: 1)Resealing and 2)Driftwood
    by scol-at-scottsdale.az.stratus.com (Scott Colbath) (9 Apr 1993)
  5. Building your own tank
    by "David W. Webb" <dwebb-at-ti.com> (27 Apr 1995)
  6. RFD: longevity of large aquaria
    by ac554-at-FreeNet.Carleton.CA (David Whittaker) (Thu, 10 Aug 1995)
  7. How To drill Holes in Tempered Glass Aquariums
    by mstone-at-dekalb.dc.peachnet.edu (michael k stone,nc113 scie,551-3115,6) (7 Dec 1996)
  8. Tempered Glass: More Than You Want To Know
    by charleyb/gr.hp.com (Charley Bay (Contract)) (Mon, 30 Oct 1995)
  9. Tempered Glass: More Than You Want To Know
    by sjmiller/mtu.edu (Steven J. Miller) (30 Oct 1995)
  10. Drilling Glass Tanks
    by tomlins/cam.org (Ed Tomlinson) (Mon, 09 Feb 1998)
  11. Aquatic Plants Digest V3 #615
    by Harvey Schneider <harvsch/earthlink.net> (Sat, 31 Oct 1998)
  12. Deconstructing an aquarium
    by IDMiamiBob/aol.com (Sat, 31 Oct 1998)
  13. Clean Glass
    by JVanrompu/aol.com (Wed, 14 Jul 1999)
  14. Aquatic Plants Digest V4 #195
    by krombhol/teclink.net (Paul Krombholz) (Sun, 2 Apr 2000)
  15. Tank Parts
    by Laura and Mark <lauramark/home.com> (Mon, 17 Apr 2000)
  16. Tempered glass
    by K9AUB/aol.com (Mon, 17 Apr 2000)

glass vs plexiglass

by marat-at-ccu.umanitoba.ca ()
Date: Thu, 13 Aug 1992


Measured light transmission of standard soda-lime glass (typical
window/aquarium glass) and poly(methylmethacrylate) acrylic -
"Plexiglass" brand.

Wavelength (nm)                % transmission
                        Glass                  acrylic

600                     90                      90
500                     92                      90
400                     93                      89
375                     90                      69
350                     78                       9
325                     20                       0
300                      0                       0

The thickness of the glass was 3 mm (glass thickness is metric in Canada)
The thickness of the acrylic was 1/8 " (ca 3 mm).

It seems that glass has better UV transmission than at least this brand
of acrylic.

Borosilicate glass (pyrex) is transparent well out into the UV (at least
to 300 nm) but I don't know if it is available in sheets at a reasonable
price.

Different types or brands of "acrylic" may be different.
If in doubt, the Chemistry Dept at  any University can put a piece
in a UV/VIS spectrophotometer and measure the transmission in about
1 min.

Kirk Marat
Dept of Chemistry
University of Manitoba
CANADA.

tank rack].

by howardr-at-col.hp.com (Howard Rebel)
Date: 16 Feb 1994
Newsgroup: rec.aquaria


This article details how I cut holes in glass without
the use of commerical drill bits.  It requires a 
drill press and copper water pipe which can be purchased
at most hardware stores.  If you are not the DIY type
skip this.

A Few Notes
-----------

You can not drill a hole in tempered glass.
You can drill a hole in untempered glass.
You can drill a hole in untempered glass and then
have it tempered.

It is more difficult to  drill holes in aquariums after
construction.

I have cut holes in 3 20 gallon and 3 40 gallon tanks without 
problems.  

How to drill a prebuilt untempered tank
---------------------------------------

	It is good pratice to glue a small square of glass 
	on the bottom side of the pane you are drilling.
	This will produce a cleaner hole and can serve to
	reinforce the glass if left in place.  
	This is esp important when drilling 10 gallon
	tanks and it makes sense to leave the square of
	glass in place to beef up the thin glass used on
	small tanks.

	Support the back side of the glass at the drill 
	location. I use a foam rubber block to push a
 	square of plywood under the drilling site.

	Place the tank on a nonflexabile surface clamped
	to the drill press.

	Keep the tank from moving by placing strips of
	wood on all four sides of the tank.


Drilling Holes for DIY Tank and Filter Builders
-----------------------------------------------

For those of you who want to drill holes in glass
and build your own aquarium the following may be of
interest.

Drill all holes prior to assembling aquarium.  This way
if you screw up you can get another piece of glass and
start over.

Buy all glass cut to size at glass shop.

Used glass is cheaper if you can find it.

Use sandpaper to dull edges.  Wear leather gloves and
work slow using a lot of care.  Note that newly cut
glass is the sharpest.  

Get a extra piece(s) of glass to practice on.

To drill holes:

	Clamp a piece of plywood to the drill table to 
	support the glass.  Screw strips of wood around 
	the glass to keep it from moving.

	Place a second piece of glass under the one you are
	cutting.  This will result in a cleaner hole.
	
	Form the well to hold the cutting grit and coolant.
	Glue a 3/4" length of 3" PVC pipe to the glass where
	you want to drill the hole.  Use silicon sealant.

	Make the bit.  Use copper pipe fittings with one or
	more notches cut into the rim (cutting edge of the
	bit).  Adaptors can be used to get from the bit size
	to the size of your chuck.

	You can also use brass tube to make bits, the notch(es)
	are still required.

	Now you need to create something to pull down on the drill
	press feed wheel.
	At first I just taped a string with a jug of water to a
	arm and adjusted the table to put the arm in a horizontal
	position.  As the bit got shorter and the hole in the glass
	got deeper the arm would move out of horizontal and the
	pressure on the bit would change.  This method works
	but you may need to reposition the table or adjust the
	quality of water in the jug.

	To over come this I cut a circle from a sheet of particle
	board and cut three slots in the face of the circle to pass 
	the arms of the drill press feed through.  I then cut a slot 
	in the edge of the circle.  This slot carries the chain
	which holds the jug.

	For cutting grit I use coarse rock tumbling grit.  Fill the
	well about half full with grit.  Add lubricant to bring the
	well to 3/4 full.  I use water for lubricant but I have
	heard that oil or antifreeze (kills cats that drink even
	a little) may work better.

	Fill the jug with water till the drill press will stay where
	you put it (bit up/down) with the motor off.

	Turn on the motor and pull down on the drill feed.  Listen
	to the sound the bit makes as you vary the pressure on the
        feed.  You will hear the grit cutting the glass when the
	pressure is correct.  

	With the drill running add water to the jug to get the cutting
	sound without you pulling down on the feed lever.

	Now let the drill do its work.  It will take anywhere between
	a few minutes to an hour depending on how well you did
	the setup.

	When the drill comes through it will retain the plug of
	glass it cut out.  Remove this plug from the bit before
	cutting additional holes.
	
	If the hole is tapered roll up a sheet of sand paper and
	ream it out.

--
Howard Rebel howardr-at-col.hp.com
FAX: 719-590-5701


tank fabrication

by dbailey-at-bcarh673.bnr.ca (Douglas Bailey)
Date: Wed, 7 Apr 1993
Newsgroup: alt.aquaria,rec.aquaria

In article <1993Apr7.021918.25096-at-doug.cae.wisc.edu>, rudolf-at-cae.wisc.edu (Rob Andrew Rudolf) writes:
|> The dimentions will be 8ft X 2ft X 2ft
|> 
|> I know that All Glass and Oceanic both make 7ft versions of this tanks but
|> I would like to know what thickness of glass to use or what thickness of 
|> acrylic.
|> 
|> Thank you.

I just happen to have a copy of "The Living Aquarium" by Peter Hunnam in my
office.  This book has a variety of information concerning the construction
of aquaria.  Unfortunately, the graph which shows glass thickness only covers
panels up to 2m long.  However, I can extrapolate easily enough.

For a panel 8ftx2ft, you would need glass 1/2 in thick for a side panel, or
3/5 in thick for the bottom of the tank.

-- 
Doug Bailey
(dbailey-at-bnr.ca)


Need Advice: 1)Resealing and 2)Driftwood

by scol-at-scottsdale.az.stratus.com (Scott Colbath)
Date: 9 Apr 1993
Newsgroup: rec.aquaria

In article <1993Apr7.173240.18886-at-zoonews.bnr.ca> dbailey-at-bcarh673.bnr.ca  
(Douglas Bailey) writes:
> In article <1993Apr7.093020.1-at-ualr.edu>, mlstrother-at-ualr.edu writes:
> |> Hi, everyone!  I've been reading the group for about a month...
> 
> welcome.
> 
> |> 
> |> 1 - I've never resealed a tank, and have just bought a used 55g which
> |>     has a leak, so am undertaking to reseal it.  I'm supposing that 
> |>     it makes more sense to do the whole tank now rather than patch
> |>     this hole now and probably have another in a new spot later?  Do
> |>     y'all agree?  Does anyone who's done this have any suggestions 
> |>     in addition to (or instead of) carefully following package directions
> |>     on the tube of sealer?  Helpful hints or warnings?  Is it maybe not
> |>     as big a deal as I'm afraid it's going to be?  (I've caulked a
> |>     bathtub before; is it much more difficult than that?)
> 
>         - More moderate suggestion: cut out all of the silicone inside 
>           the tank, but leave that which is gluing the glass together, 
>           then re-seal all inside corners (the original silicone acts 
>           as glue, the new silicone acts as a seal, and it doesn't 
>           matter if they bond together).  

The above suggestion is what I did on my 55 gal for the office and it worked  
like a charm. I would suggest that the old silicone be removed with a straight  
edge razor and make sure to get every last bit out of all the corners and  
joints. The better you do preping the tank, the more likely it is that it will  
remain leak free. Apply two coats. The first being *very* thin, acting as a  
filler for the joints and corners, and a second heavier coat to spread the  
silicone over a wider area. Mash the silicone in with your finger. You will  
find that it spreads very nicely. Take your time, do a good job. Test for leaks  
after the silicone cures. I filled my tank in the garage in %25 increments over  
two days until it was full, constantly looking for leaks. I found none. 


|> Thanks for any help!  And thanks for being here.  It's great to find
|> kindred souls!

I agree %100.

**********************************************************
Scott Colbath
Stratus Computer
Phoenix, Az.  (602)852-3106
Internet:scott_colbath-at-az.stratus.com


Building your own tank

by "David W. Webb" <dwebb-at-ti.com>
Date: 27 Apr 1995
Newsgroup: alt.aquaria,rec.aquaria,sci.aquaria

charlysue-at-aol.com (Charlysue) wrote:
>
> My boyfriend and I have just finished setting up a 90 gal. tank.  It is
> still cycling, but we would like another one and are thinking about
> building it ourselves.  I was wondering if anyone had any information
> about this process, or if anyone knows of any books that could help us
> out.  Any help would be appreciated.
> Charlene

This post is intended as a general note of caution for all who plan
to build aquariums.  

My sister-in-law used to work as a sales representative for a corporate
medical services supplier in the Dallas area.  One of her customers
was Oceanic Aquariums in Garland.  When my family went out to lunch
for someone's birthday, she'd always have a story about one of the 
many times she'd been to Oceanic, and about the kind of accidents 
that they occasionally had (over two years ago, I don't know about now).
She'd tell us about people who had the glass slip on them because they
weren't handling it properly.  They'd sever fingers, get all the skin
and muscle peeled off of one side of their arm, and lots of other 
nasty injuries.  

Please be careful when working with glass.

Regards,

---------------------------------------------------------
David W. Webb                                            
dwebb-at-ti.com                                             
                                                         
Any correlation between my opinions and those of Texas   
Instruments is purely coincidental.  (I don't speak for  
TI)                                                      
---------------------------------------------------------



RFD: longevity of large aquaria

by ac554-at-FreeNet.Carleton.CA (David Whittaker)
Date: Thu, 10 Aug 1995
Newsgroup: alt.aquaria


Keith Lookingland (lookingl-at-pilot.msu.edu) writes:
> In a recent conversation with the owner of my local aquarium store I was 
> told that large aquaria (say < than 100 gal) have a "half-life" of about 15 
> years.  Evidently, the silicone sealant fatigues over time resulting in loss 
> of the intergrity of the bond between the glass sides.  This is the first 
> time I have heard of this and wondered if anyone out there in the net has 
> had a problem with older, large aquaria?  If there is fatigue does it result 
> in a "repairable" small leak, or is there a massive "falling apart" of the 
> aquarium with the resultant loss of fish and living room furniture, etc.?  
> If this is true, then I would be hesitant to purchase "used" large aquaria 
> through the classified ads.  On the other hand, this just may be a ploy by 
> this aquarium store owner to sell new equipment!

He is correct with respect to older tanks. You should see a stretching of
the silicone first. I saw this on the 125 gallon tank of a friend which
he had bought used. You can always re-glue the glass panes after scrapping
off the old sealant. Newer sealant is good for about 50 years I believe.
Depends upon the product.

Dave
--
 


How To drill Holes in Tempered Glass Aquariums

by mstone-at-dekalb.dc.peachnet.edu (michael k stone,nc113 scie,551-3115,6)
Date: 7 Dec 1996
Newsgroup: rec.aquaria.freshwater.cichlids


In a previous article, mlkabat-at-gte.net ("Mike Kabat") says:

>What are the tools and techniques needed to drill  holes in tanks for
>external filters etc?
>This is for tempered glass tanks 10-55 gal.
>
>

A special glass drilling bit is needed to drill holes in glass tanks.  It 
looks similar to a hole saw used to drill holes in wood, but instead of being 
serrated along the cutting edge, it has a smooth edge with diamond dust  
embedded in it.  These bits are not cheap.  I got a 1 3/4" bit (for 1" 
bulkhead fitting) from a company called Somer & Maca for about $65.OO.  This 
was the economy model with a single layer of dust.  The industrial bit, 
which has a thicker coating, was almost three times as much.  The bit mounts 
in a regular hand drill (variable speed is best).  The bit doesn't really 
"cut" the glass, it actually grinds a circular hole through the glass.  Somer 
& Maca also sell a coolant to squirt on the glass that will extend the life of 
the bit.  

As far as the actual process of drilling, it is not that difficult with a 
little practice.  Getting the initial groove in the glass started is the 
hardest part, since the bit has a tendency to "skate" across the smooth glass 
surface.  I have had the most luck by starting off at about a 45 degree angle 
to start the initial groove and gradually increasing the angle until the bit is 
perpendicular to the glass.  After that, you just wait for the bit to do its 
job.  Don't be tempted to push the bit like you would if you were drilling in 
metal or wood, all you will do is break the glass.  Let the weight of the 
drill push the bit through.  It takes me about 3-5 minutes to drill through 
1/4" plate glass.

A word of caution on TEMPERED glass.  The conventional wisdom is that you 
CAN'T DRILL tempered glass.  I have managed to drill a few (1 or 2) tempered 
tanks with success, but I've had many crack.  So, I don't recomend drilling 
tempered glass.

Hope this is of use,
M. Stone



Tempered Glass: More Than You Want To Know

by charleyb/gr.hp.com (Charley Bay (Contract))
Date: Mon, 30 Oct 1995
Newsgroup: sci.aquaria,rec.aquaria,alt.aquaria

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 and tempering steel are roughly the same
processes:

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).

--
--charley                              #include <stdisclaimer.h>
charleyb-at-gr.hp.com    -or-    charley-at-agrostis.nrel.colostate.edu



Tempered Glass: More Than You Want To Know

by sjmiller/mtu.edu (Steven J. Miller)
Date: 30 Oct 1995
Newsgroup: sci.aquaria,rec.aquaria,alt.aquaria

Charley- good job clarifying this bit.  I have wondered when someone would
actually do a little research on it.  Most of the posts up to this time
were in error.  I would just like to summarize it, and clarify one point.

You are right on when you say that tempering the glass is
done by quenching the outer surfaces from red hot, and they shrink rapidly.
The inside is still soft and deforms to match the dimensional change on the
outside.  The inside then cools the rest of the way, and tries to shrink.
(thermal contraction is neat.)  The outside won't let it shrink (as it is
already cool and can't deform).  Therefore, the outside is in compression, 
and the inside is in tension.  This is great for resisting cracks because
cracks only propagate under tensile stresses.  Since the surface is under
large compressive stresses, any small flaws that would propagate through
untempered glass are, in effect, held shut by this compressive layer.  In
order to break, the stress on the surface must be tensile, and the applied
stress must be sufficient to overcome the residual compressive stress and
then propagate a crack.  This is a great principle, and the use of residual
compressive stresses on surfaces of objects to prevent crack propagation is
used on many other parts, one of the more common being valve springs in
engines (compressive stresses not applied via tempering).

That being said-
The process of tempering glass is absolutely nothing at all like that of
tempering steel :^)  Tempering steel is done by heating a previously quenched
piece in order to induce a phase transformation, and alter the crystal
structure of the steel into one that consists of many tiny carbide
particles (which are very hard,) and they are surrounded by basically an
iron phase.  This way, cracks trying to go through steel have to go around
and/or through carbide particles, and also tear apart the iron matrix the
carbides are embedded in.

Steve

Charley Bay (Contract) (charleyb-at-gr.hp.com) wrote:
: 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 and tempering steel are roughly the same
: processes:
: 
: 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).
: 
: --
: --charley                              #include <stdisclaimer.h>
: charleyb-at-gr.hp.com    -or-    charley-at-agrostis.nrel.colostate.edu
: 


Drilling Glass Tanks

by tomlins/cam.org (Ed Tomlinson)
Date: Mon, 09 Feb 1998
Newsgroup: rec.aquaria.marine.misc,rec.aquaria.marine.reefs,rec.aquaria.tech

In <6bktjg$vcu$3-at-isn.dac.neu.edu>, ptimlin-at-lynx02.dac.neu.edu (patrick timlin) writes:
>Mornay Durant (mornayd-at-dial.pipex.com) wrote:
>: Can anyone tell me how to drill a glass tank?  Are there special ways of
>: doing so?  What kind of drill bit should I use?  Should I drill a small hole
>: and then larger and larger, or can I just drill the right size to start
>: with?
>
>You do not drill glass really, at least not like you do with wood or metal
>where you might work your way up on hole sizes.  Glass drilling is more of
>a grinding process and you grind out a circle the size of the hole you
>want.  So when you are done you have a little round piece of glass that
>went where you hole is now.  Much like when you cut a hole in a door for a
>door knob or dead bolt lock.
>
>I haven't done any myself, so I can not offer any real life tips or
>advice.  You might check with a local glass shop and see what they charge
>to cut a hole for your tank.

This is exactly how it works.  I have done it many times.  It takes about 15 
minutes to go though 1/4 inch glass.  You build a ridge (kids plasacine works 
fine) around the area you want to drill, add grit and water and grind with the
bit until most of the water is gone.  Then you add more water and grit and
continue.  Its lots faster if you can get a diamond bit but those cost much
more.  In order to keep the bit at the same orientation I adapted a cheap drill
press (one of those designed for 3/8 in chucks).

BTW, get the tank adaptor first.  Measure the size of the hole needed using
this.  Suspect that you tank you will need a 1.75 inch or larger hole.  I 
would recommend a minimum of 1 inch ID tubing for a drain and larger would
not hurt.

Luck,

Ed Tomlinson, Montreal, Canada
Home: tomlins at cam dot org    

To obtain my public key mail me with a subject of: PGP Key



Aquatic Plants Digest V3 #615

by Harvey Schneider <harvsch/earthlink.net>
Date: Sat, 31 Oct 1998

> Subject: Re: Deconstructing an aquarium
>
> John M. Burns asked....
>
> >There have been numerous posts about using silicone to assemble and fix
> >aquariums and other things.  My problem is just the opposite.  I want to
> >take one apart, a 75 gallon one.  Problem is, I can scrape all the
> >accessible silicone out, but that thin seam where the two pieces of glass
> >"connect" is impossible to get to.  Does anyone know of a solvent that will
> >soften or dissolve silicone (without destroying the plastic frame)?  Any
> >suggestions welcome.  TIA.  -John
>

Commercially lye dissolved in tetra hydro furan is used to remove cured silicon
rubber. this is extremely nasty stuff and will probably dissolve the plastic
frame. I have personally disassembled tanks for repair by dragging a double edged
razor blade through the seam with a pair of vise grip pliers. I then used a razor
blade scraper to remove all of the silicon rubber from the glass so that the tank
could be reassembled. This is important since the silicon rubber does not bond
well to itself.
Harvey Schneider

------------------------------


Deconstructing an aquarium

by IDMiamiBob/aol.com
Date: Sat, 31 Oct 1998

In a message dated 10/31/98 1:59:31 PM Mountain Standard Time, Aquatic-Plants-
Owner@actwin.com writes:

> >There have been numerous posts about using silicone to assemble and fix
>  >aquariums and other things.  My problem is just the opposite.  I want to
>  >take one apart, a 75 gallon one.  Problem is, I can scrape all the
>  >accessible silicone out, but that thin seam where the two pieces of glass
>  >"connect" is impossible to get to.  Does anyone know of a solvent that
will
>  >soften or dissolve silicone (without destroying the plastic frame)?  Any
>  >suggestions welcome.  TIA.  -John
>  
Try getting a very thin wire in the gap at the exposed end (the top) between
the front and side pane.  Push the two pieces away from one another while a
parnter pulls the wire down from inside and out.  It will cut through the
silicone.  Once you get through the edges at left and right, you can just tip
the front down and rip the bottom joint.  From there it is self-evident.

------------------------------


Clean Glass

by JVanrompu/aol.com
Date: Wed, 14 Jul 1999

In a message dated 7/13/99 2:55:46 PM Central Daylight Time, 
Aquatic-Plants-Owner@actwin.com writes:

<< Does anyone have a magic pill for keeping cover glass clean?  I feel I 
need 
 to keep glass on the tank because of the rapid evaporation, but I can't seem 
 to get it very clean anymore.  Should I just replace the glass every year or 
 so?
 
 It seems such a pity to have a hood packed full of full spectrum lighting 
 and then lose so much of that light to dirty glass.
 
 TIA >>

The old standby - Vinegar - works extremely well, it gets rid of all those 
white stains and buildup the coats glass, aquarium heaters etc.

Regards

John


Aquatic Plants Digest V4 #195

by krombhol/teclink.net (Paul Krombholz)
Date: Sun, 2 Apr 2000

>>Wright Huntley wrote:

>.....Back to the redeposited glass... When the glass surface is rough, cerium
>oxide or rouge are not effective agents for fixing it. You need to start
>with a grinding compound (silicon carbide or diamond), and a tool that
>doesn't trap it (cast iron or glass). Grind the surface flat and smooth,
>first. Gradually wash off and reduce the size of the grinding compound
>particles to get a smoother and smoother surface. Go down to at least as
>small as 5 microns for the final grind particle size. Then switch to a tool
>that *does* trap the cerium oxide or jewelers rouge (hard wax or pellon pad)
>for the polish stage. Glass is too cheap for this much fuss (apologies to
>starving students, of course).
>

Well, I am a starving professor, and can't afford to do that, even though
it sounds like the only way to do it if I had to polish off the deposited
glass.  I think I will try a coating with spray on acrylic.  Hopefully,
there won't be anything toxic in the acrylic.

Bob Dixon wrote:
>...........but how come I can get
>the stuff off the underside of my cover?  How come the rest of us aren't
>experiencing this "redeposited glass" thing?  What's so different about
>Mississippi water that you are seeing this and I'm not?
>
>The carbonate buildup in a pot that is used to boil water is not soft, it is
>rock hard.  Maybe your lights are baking the stuff on?  I'd still try the
>CLR, and if it comes off, it is carbonates.
>
It is not a difference in the water.  It is probably a difference on how
much air circulates under the cover.  I have covers that cover the entire
tank with no air circulation.  The lights sit on the cover and heat up the
top layer of the water.  When the lights go off, the cover cools, and there
is extensive condensation on the cover from the warm water, below.  When
the lights go on in the morning, this condensed water dries up.  Repeating
this cycle daily builds up in several months a noticable silica deposit.  I
would think that you may have more air circulating under your covers, so
that you don't get very much condensation on them.


The same sort of fogging of glass due to dissolving and redepositing can
occur in the double windows that the newer houses are equipped with if
these windows develop a leak and get some water inside.  As the temperature
cycles during each day, there is condensation and then evaporation, and
after a year or less, the glass is badly fogged by the etching and
redepositing.  I have seen windows in this condition when I was
house-hunting, and the house we finally purchased had two fogged windows
that we required the seller to replace.

The deposit really is silicon dioxide, and silicon dioxide is slightly
soluble in water.  It can be removed from silicates in the presence of
carbon dioxide or bicarbonates.  My limnology text says that natural waters
can contain "milligrams to centigrams" of silicic acid.

I have also had calcium carbonate deposits on my tank covers, and they are
easy to remove.  Compared to the silica deposits, they are not hard.

Paul Krombholz, in Central Mississippi, where we are getting
drought-busting rains, starting yesterday.  At least 2 inches, so far.  The
frogs love it!


Tank Parts

by Laura and Mark <lauramark/home.com>
Date: Mon, 17 Apr 2000

You can buy glass lid hinges and backstrips from Pet
Warehouse "All-Glass brand". You can also buy Tank top
frames and bottom frames From ALL-Glass Aquarium through
your LFS providing your tank is either their brand or has
the same measurements and glass thickness.


Tempered glass

by K9AUB/aol.com
Date: Mon, 17 Apr 2000

In a message dated 4/17/2000 01:09:07 Pacific Daylight Time, 
Aquatic-Plants-Owner@actwin.com writes:

> Typically, modern tempered 
>  glass is marked as such in a corner.  Older tempered glass may not be.  An 
>  experienced glass technician can tell by the "ring" of the glass if it is 
>  tempered by tapping it.

There is a more certain way.  Take two photographic polarizing filters.  
Sandwich them together.  Rotate one of the filters.  Light transmitted 
through the filters will fade from lighter to completely blacked out as the 
planes of the polarized material crosses through each other's axis.  Now, try 
the same thing with the piece of glass sandwiched between the two filters, 
and rotate one of the filters.  If the glass in untempered, the light 
transmitted through the filters will act the same way, fading from lighter to 
blacked out.  If the glass IS tempered, an interesting phenomena will occur:  
as the filters are rotated, a black cross will form through the filters.  
It's an unmistakable sign:  if the cross is there, the glass is tempered.
  


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This page was last updated 30 July 2000