Samuel T DREW on mon 30 mar 98
Hi folks!
Wanting to hear from people who have experimented with cullet glazes.
I am undertaking some experiments, but have found that crazing is a
problem. I've added zinc which has helped to flux my original recipe
out, it evetually crazed after ripping them from the kiln at 300c
(not a wise move). I know frits are more versatile and generally
craze free, but cullet is, oh so, much cheaper. Plus I find there
must be some iron and copper contamination.
Any comment, questions, or suggestions, or recipes graciously welcome
sam
Oz
David Hendley on tue 31 mar 98
Sam,
A cullet glaze is not a special glaze type. Many glazes could
be reformulated to use cullet, and a cullet glaze could be
reformulated to eliminate or reduce the cullet.
Sodium is the main flux in cullet. Sodium has the highest
expansion of all the fluxes, therefore a glaze is likely to craze
if it uses a high percentage of cullet. Cullet also adds silica
and some calcium and maybe some magnesium to the glaze.
The most valuable use for cullet, and how I use it, is in slip
glazes. Since these types of glazes have a high percentage of
clay, I want a sodium flux source that is also low in alumina,
since the clay already supplies a lot of alumina. Cullet fills the
bill. Feldspar is an easier and cheaper choice if the extra alumina
it adds to the mix is not a problem. I've never used more than
15% glass cullet in a glaze, and my glazes are craze-free.
At the 15% level, I can't tell that the cullet is adding any iron or
copper. In fact, I can tell no difference in my glaze if the cullet
was made from clear glass, brown glass, or green glass.
Happy grinding and ball-milling,
David Hendley
Maydelle, Texas
hendley@sosweb.net
At 09:23 AM 3/30/98 EST, you wrote:
>----------------------------Original message----------------------------
>Hi folks!
>Wanting to hear from people who have experimented with cullet glazes.
>I am undertaking some experiments, but have found that crazing is a
>problem. I've added zinc which has helped to flux my original recipe
>out, it evetually crazed after ripping them from the kiln at 300c
>(not a wise move). I know frits are more versatile and generally
>craze free, but cullet is, oh so, much cheaper. Plus I find there
>must be some iron and copper contamination.
>Any comment, questions, or suggestions, or recipes graciously welcome
>
>sam
>Oz
>
Louis Katz on tue 31 mar 98
cullet glaze
Cone 2 3 4 5 6
Ingredient Amount
container Glass 49.01
Redart 6.24
EPK 9.47
Dolomite 2.68
Whiting 21.19
Silica 11.42
Total 100.01
Molecular Formula:
0.279 KNa0 0.122 Al2O3 1.985 SiO2
0.590 CaO 0.007 Fe2O3 0.003 TiO2
0.128 MgO
This recipe is simlar in terms of unity to one in use in Thailand.
I have no idea about its durability. Perhaps some one else can speak to
this.
Certainly there is a lot of variation in container glass.
Louis
Tony Hansen on wed 1 apr 98
The most transparent and cleanest glaze I ever made was based on
cullet. Unfortunately, as others have observed, it crazed badly.
However if you have the formula for your cullet and the supplier
blends or selects to maintain it you can treat it exactly as if
it was a high sodium frit. Just enter it into the materials
database of your glaze calculation software and use it in any
glaze currently employing nepheline or soda feldspar.
--
T o n y H a n s e n thansen@digitalfire.com
Don't fight the glaze dragon alone
INSIGHT, Magic of Fire at http://digitalfire.com
nikom chimnok on sat 4 apr 98
We formerly used a cullet glaze with the following formula:
1 local clay
2 ashes
3 cullet
It only crazed if applied very thick, though it sometimes is crazing
in delayed fashion, I can see a couple years later.
But one thing to point out is that this glaze was used with
essentially an earthenware clay, which shrank 5% between the bisque and
glaze firings. That is, as bisque, it had already shrunk 12%, and then in
the end it shrank 17% when fired to cone 7.
Nikom
koratpot@loxinfo.co.th
Karl P. Platt on fri 17 apr 98
I am working on a project which aims to recycle about 2,000 tons/year of
recycled bottles into ceramic glaze frit. Recycling glass is nowhere
near a cost-effective thing to do under any circumstances, but being a
capitalist, I am not beyond taking advantage of the cheap money
available to undertake such initiatives whatever the mistaken feel-good
premesis are for making such funds available. All that said I read a
30.3.98 article posted here by a fellow from Oz with interest.
Scrap glass can be used successfully in ceramic glazes with little
difficulty. It does, however, need to be ground, which greatly increases
the amount of surface area/unit weight available for reaction with water
in the slip. Bottle glass is best as it has the least solubility.
Hand-shop glass can cause problems with slip stability owing to soluble
alkali.
Consider that a typical bottle glass composition is roughly:
15 Na2O, 10CaO, 74 SiO2, 1 Al2O3.
This material can be added to an extent that the glaze composition
requires alkali -- usually not much more than 7% or so is present in a
garden variety glaze. There will, of course, be variations. The rest of
the glaze components can be furnished as the usual group of clays,
oxides or carbonates used.
Cullet is free in most places -- go to any glass shop and take their
trim. Anywhere that has a recycling program has a *mountain* of glass as
there is no possible way to use it all -- this is another discussion
entirely.
Many commercial glasses are made with fairly trashy sand- it has enough
Fe in it to be green -- and many commercial glasses are melted in
furnaces paved with Cr2O3 refractories given that these have the highest
resistance to corrosion by the molten glass. The presence of Cr,
naturally, imparts a green tint to the glass. This can be covered over
by adding other oxides, but the results will likely be a bit dingy.
KPP
McCoy, Jack Eugene on tue 21 apr 98
Does anyone have any ideas for crushing glass in small amounts?
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
=-=-=-=-=
Jack McCoy
Systems Programmer
East Carolina University
Voice: (919) 328-6855
Email: mccoyj@mail.ecu.edu
> ----------
> From: Karl P. Platt[SMTP:kplatt@glass.com]
> Reply To: Ceramic Arts Discussion List
> Sent: Friday, April 17, 1998 8:01 AM
> To: Multiple recipients of list CLAYART
> Subject: Cullet Glaze
>
> ----------------------------Original
> message----------------------------
> I am working on a project which aims to recycle about 2,000 tons/year
> of
> recycled bottles into ceramic glaze frit. Recycling glass is nowhere
> near a cost-effective thing to do under any circumstances, but being a
> capitalist, I am not beyond taking advantage of the cheap money
> available to undertake such initiatives whatever the mistaken
> feel-good
> premesis are for making such funds available. All that said I read a
> 30.3.98 article posted here by a fellow from Oz with interest.
>
> Scrap glass can be used successfully in ceramic glazes with little
> difficulty. It does, however, need to be ground, which greatly
> increases
> the amount of surface area/unit weight available for reaction with
> water
> in the slip. Bottle glass is best as it has the least solubility.
> Hand-shop glass can cause problems with slip stability owing to
> soluble
> alkali.
>
> Consider that a typical bottle glass composition is roughly:
>
> 15 Na2O, 10CaO, 74 SiO2, 1 Al2O3.
>
> This material can be added to an extent that the glaze composition
> requires alkali -- usually not much more than 7% or so is present in a
> garden variety glaze. There will, of course, be variations. The rest
> of
> the glaze components can be furnished as the usual group of clays,
> oxides or carbonates used.
>
> Cullet is free in most places -- go to any glass shop and take their
> trim. Anywhere that has a recycling program has a *mountain* of glass
> as
> there is no possible way to use it all -- this is another discussion
> entirely.
>
> Many commercial glasses are made with fairly trashy sand- it has
> enough
> Fe in it to be green -- and many commercial glasses are melted in
> furnaces paved with Cr2O3 refractories given that these have the
> highest
> resistance to corrosion by the molten glass. The presence of Cr,
> naturally, imparts a green tint to the glass. This can be covered over
> by adding other oxides, but the results will likely be a bit dingy.
>
> KPP
>
Carl meigs on wed 22 apr 98
Jack ,
Just for historical curiosity, you might be interested in how the old Seagrove
potters crushed glass using nearby stream waterpower. Look it up in
"Turners and Burners."
I would combine using shop glasses for eye protection with something like
a mortar and pestle. Stand back.
At 07:32 AM 4/21/98 EDT, you wrote:
>----------------------------Original message----------------------------
>Does anyone have any ideas for crushing glass in small amounts?
>
>
>=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>=-=-=-=-=
>Jack McCoy
>Systems Programmer
>East Carolina University
>Voice: (919) 328-6855
>Email: mccoyj@mail.ecu.edu
>
>
>
>
>> ----------
>> From: Karl P. Platt[SMTP:kplatt@glass.com]
>> Reply To: Ceramic Arts Discussion List
>> Sent: Friday, April 17, 1998 8:01 AM
>> To: Multiple recipients of list CLAYART
>> Subject: Cullet Glaze
>>
>> ----------------------------Original
>> message----------------------------
>> I am working on a project which aims to recycle about 2,000 tons/year
>> of
>> recycled bottles into ceramic glaze frit. Recycling glass is nowhere
>> near a cost-effective thing to do under any circumstances, but being a
>> capitalist, I am not beyond taking advantage of the cheap money
>> available to undertake such initiatives whatever the mistaken
>> feel-good
>> premesis are for making such funds available. All that said I read a
>> 30.3.98 article posted here by a fellow from Oz with interest.
>>
>> Scrap glass can be used successfully in ceramic glazes with little
>> difficulty. It does, however, need to be ground, which greatly
>> increases
>> the amount of surface area/unit weight available for reaction with
>> water
>> in the slip. Bottle glass is best as it has the least solubility.
>> Hand-shop glass can cause problems with slip stability owing to
>> soluble
>> alkali.
>>
>> Consider that a typical bottle glass composition is roughly:
>>
>> 15 Na2O, 10CaO, 74 SiO2, 1 Al2O3.
>>
>> This material can be added to an extent that the glaze composition
>> requires alkali -- usually not much more than 7% or so is present in a
>> garden variety glaze. There will, of course, be variations. The rest
>> of
>> the glaze components can be furnished as the usual group of clays,
>> oxides or carbonates used.
>>
>> Cullet is free in most places -- go to any glass shop and take their
>> trim. Anywhere that has a recycling program has a *mountain* of glass
>> as
>> there is no possible way to use it all -- this is another discussion
>> entirely.
>>
>> Many commercial glasses are made with fairly trashy sand- it has
>> enough
>> Fe in it to be green -- and many commercial glasses are melted in
>> furnaces paved with Cr2O3 refractories given that these have the
>> highest
>> resistance to corrosion by the molten glass. The presence of Cr,
>> naturally, imparts a green tint to the glass. This can be covered over
>> by adding other oxides, but the results will likely be a bit dingy.
>>
>> KPP
>>
>
>
meigs@neca.com
Mudnjoy on wed 22 apr 98
Crushing glass in small amounts: I use a hammer with the glass between
newspaper & I run it through a screen.
Louis Katz on wed 22 apr 98
McCoy, Jack Eugene wrote:
>
> ----------------------------Original message----------------------------
> Does anyone have any ideas for crushing glass in small amounts?
>
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Heat the Glass up to just as it starts to deform in a wire cage.
Quench the glass in water.
Grind in a ball mill with 1" steel shot. Use the steel shot only if you don't
care about the amount of iron in the cullet.
Of course don't short your electric kiln with your wire cage. Wear safety
glasses, etc.
Louis
Fay & Ralph Loewenthal on fri 24 apr 98
I use a mortar and pestle wrapped in a plastic bag, with the
opening of the bag wrapped around the handle of the
pestle. I have had too many bits of flying glass coming too
close for comfort to my eyes. I wear specs, and have learnt
how dangerous flying glass can be. Hope this helps Ralph
in PE SA
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