Lee Love on fri 13 aug 10
On Fri, Aug 13, 2010 at 7:19 PM, Randy McCall wrote:
> Is there anything I need to know before I melt some glass in the bottom o=
=3D
f some bowls at Cone 6?
>
> Just asking before I try it.
Do a lot of tests on different glass. Clear glass can sometimes burn
black. It is a mainstay of Kevin Caufield's work.
--=3D20
--
=3DA0Lee, a Mashiko potter in Minneapolis
http://mingeisota.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
marci and rex on fri 13 aug 10
At 07:19 PM 8/13/2010, Randy McCall wrote:
>Is there anything I need to know before I melt some glass in the
>bottom of some bowls at Cone 6?
>
Cool slowly ...
marci the chinapainter..
Randy McCall on fri 13 aug 10
Is there anything I need to know before I melt some glass in the bottom of =
=3D
some bowls at Cone 6?
=3D20
Just asking before I try it.
Randy
=3D
Robert Harris on fri 13 aug 10
The biggest problem I've seen is that if it's too thick it can craze
in such a way as to split leaving nasty sharp edges, or even pop out.
Anything thicker than 0.5cm may be a problem. It's possible that
firing down - or soaking at a particular temp (anyone else here
suggest what temp?) could smooth over the edges.
Robert
On Fri, Aug 13, 2010 at 8:19 PM, Randy McCall wrote:
> Is there anything I need to know before I melt some glass in the bottom o=
f some bowls at Cone 6?
>
> Just asking before I try it.
>
> Randy
>
>
--
----------------------------------------------------------
William & Susan Schran User on fri 13 aug 10
On 8/13/10 8:19 PM, "Randy McCall" wrote:
> Is there anything I need to know before I melt some glass in the bottom o=
f
> some bowls at Cone 6?
> Just asking before I try it.
> Randy
As long as you are melting the glass inside a bowl, should be fine.
I would advise against doing this for functional ware.
The glass will not fit the clay as a glaze does and will certainly craze.
During cooling the glass may also fracture.
Should the glass come into contact with hot or cold liquids/food, additiona=
l
fracturing may occur causing fragments to separate.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
James Freeman on fri 13 aug 10
On Fri, Aug 13, 2010 at 8:19 PM, Randy McCall wrote:
> Is there anything I need to know before I melt some glass in the bottom o=
=3D
f some bowls at Cone 6?
Randy...
I'm certainly no expert, but I think I can offer a few clues.
Coincidentally, I just melted piles of marbles in the bottom of some
bowls in my makeshift raku kiln this past weekend. First, I think
cone 6 is WAY too hot. Our marbles were nicely melted at 1575 F. I
think the maximum temperature for casting glass, which is essentially
what you are doing, is somewhere around 1740 F. Think of the glass as
a very low fire glaze, which is essentially what it is. What happens
when you run a typical low fire glaze up to cone 6? I think you will
end up with a lot of frozen, broken bubbles with very sharp edges, but
that is just a guess.
I did nothing special with my melted glass, since it was just playing
around to satisfy my niece's curiosity. I yanked the glass-filled
bowls from the raku kiln (the glass was about the consistency of
molasses, and 1/2" to 1" thick), set them in the reduction barrel for
about 10 minutes, then quenched them in water. Thus, there was no
annealing step at all. As Robert surmised, the cast glass did crack,
though not sharply nor dangerously. I would characterize it as
something less than a crack, but definitely more than crazing. It is
quite beautiful, but very far from functional.
To do it correctly, one should hold for a bit at top temperature to
insure a complete melt, but then the kiln needs to be crash cooled
(very quickly, through repeatedly opening the lid for a drop of 70
degrees or so, then shutting the lid briefly to allow temps to even
back out a bit) down to the annealing temperature of 1040 F in order
to avoid devitrification. The kiln then needs to be held for many
hours at 1040 (probably 4-8). After the long annealing, you need to
cool VERY slowly, through the stress point, all the way to room
temperature.
There are many variables, depending on such things as the composition
of your glass and how thick your glass will be, but the above will
give you a general idea of what's involved. Also, bear in mind that
the above is a simplification for the sake of brevity. A really good
book for this and many other warm glass techniques is Warm Glass, by
Philippa Beveridge, et al. The ISBN is 1-57990-655-9.
Just my thoughts. Good luck with your project.
...James
James Freeman
"All I say is by way of discourse, and nothing by way of advice.=3DA0 I
should not speak so boldly if it were my due to be believed."
-Michel de Montaigne
http://www.jamesfreemanstudio.com
http://www.flickr.com/photos/jamesfreemanstudio/
http://www.jamesfreemanstudio.com/resources
James Freeman on sat 14 aug 10
A fellow clayart member informed me off list that he has fired glass
to cone 10 without significant bubbling, as the glass was already
de-gassed during it's manufacture. He advised thinking of the glass
as a frit at those temperatures. He said the glass is extremely fluid
at high temperature, and will flow like water from any small crack in
your piece.
Take care.
...James
James Freeman
"All I say is by way of discourse, and nothing by way of advice.=3DA0 I
should not speak so boldly if it were my due to be believed."
-Michel de Montaigne
http://www.jamesfreemanstudio.com
http://www.flickr.com/photos/jamesfreemanstudio/
http://www.jamesfreemanstudio.com/resources
On Fri, Aug 13, 2010 at 10:52 PM, James Freeman
wrote:
> On Fri, Aug 13, 2010 at 8:19 PM, Randy McCall wrote:
>
>> Is there anything I need to know before I melt some glass in the bottom =
=3D
of some bowls at Cone 6?
>
>
>
>
> Randy...
>
> I'm certainly no expert, but I think I can offer a few clues.
>
> Coincidentally, I just melted piles of marbles in the bottom of some
> bowls in my makeshift raku kiln this past weekend. =3DA0First, I think
> cone 6 is WAY too hot. =3DA0Our marbles were nicely melted at 1575 F. =3D=
A0I
> think the maximum temperature for casting glass, which is essentially
> what you are doing, is somewhere around 1740 F. =3DA0Think of the glass a=
s
> a very low fire glaze, which is essentially what it is. =3DA0What happens
> when you run a typical low fire glaze up to cone 6? =3DA0I think you will
> end up with a lot of frozen, broken bubbles with very sharp edges, but
> that is just a guess.
>
> I did nothing special with my melted glass, since it was just playing
> around to satisfy my niece's curiosity. =3DA0I yanked the glass-filled
> bowls from the raku kiln (the glass was about the consistency of
> molasses, and 1/2" to 1" thick), set them in the reduction barrel for
> about 10 minutes, then quenched them in water. =3DA0Thus, there was no
> annealing step at all. =3DA0As Robert surmised, the cast glass did crack,
> though not sharply nor dangerously. =3DA0I would characterize it as
> something less than a crack, but definitely more than crazing. =3DA0It is
> quite beautiful, but very far from functional.
>
> To do it correctly, one should hold for a bit at top temperature to
> insure a complete melt, but then the kiln needs to be crash cooled
> (very quickly, through repeatedly opening the lid for a drop of 70
> degrees or so, then shutting the lid briefly to allow temps to even
> back out a bit) down to the annealing temperature of 1040 F in order
> to avoid devitrification. =3DA0The kiln then needs to be held for many
> hours at 1040 (probably 4-8). =3DA0After the long annealing, you need to
> cool VERY slowly, through the stress point, all the way to room
> temperature.
>
> There are many variables, depending on such things as the composition
> of your glass and how thick your glass will be, but the above will
> give you a general idea of what's involved. =3DA0Also, bear in mind that
> the above is a simplification for the sake of brevity. =3DA0A really good
> book for this and many other warm glass techniques is Warm Glass, by
> Philippa Beveridge, et al. =3DA0The ISBN is 1-57990-655-9.
>
> Just my thoughts. =3DA0Good luck with your project.
>
> ...James
>
> James Freeman
>
> "All I say is by way of discourse, and nothing by way of advice.=3DA0 I
> should not speak so boldly if it were my due to be believed."
> -Michel de Montaigne
>
> http://www.jamesfreemanstudio.com
> http://www.flickr.com/photos/jamesfreemanstudio/
> http://www.jamesfreemanstudio.com/resources
>
Vivianne Escolar on sat 14 aug 10
I did this succesfully using an 06 comercial clear glaze and then
laid broken stained glass in blue, green, red and yellow. It came
out really good! This was for a piece I did of a lady sitting in a
pond. It looked just like a pond. I applied the comercial glaze
following instructions on the label, laid the glass at the bottom, in
small groups and single layered according to colour. When it melted it
fused to the glaze and where the colours met I got other shades making
it look rainbowie. I have also used the one colour and the effect is
really nice. Only for decorative pieces though. Hope this helps.
Vivianne Escolar
viviescol@gmail.com
On Aug 13, 2010, at 10:57 PM, marci and rex wrote:
> At 07:19 PM 8/13/2010, Randy McCall wrote:
>> Is there anything I need to know before I melt some glass in the
>> bottom of some bowls at Cone 6?
>>
>
> Cool slowly ...
> marci the chinapainter..
paul gerhold on sat 14 aug 10
Randy,
It is very important to use glass from wine bottles since drinking good win=
e
is one of the benefits of exploring this technique. Another way to do this
which will yield somewhat different results is to do the cone 6 firing firs=
t
and then refire with the glass to about 1600.
Do not ever do this for functional since there will probably be crazing and
even if there is no initial crazing the piece will have crazing over time .
Also best color for use with clear glass is copper which does lovely
turquoise. Another thing to explore is using colored rods or chips from
glass suppliers and just melt into a glaze so glass areas are raised and ca=
n
be made into patterns. You can use glass pieces on vertical surfaces if yo=
u
use dots of wet glaze to stick the pieces. Glass tack does not work as
well. If you really want to go far out you can use the same techniques use=
d
to make sand Mandalas to apply glass powder on a flat surface making some
very detailed designs.
Paul
Vince Pitelka on sat 14 aug 10
Several people have mentioned crazing, and it is important to point out tha=
t
crazing in itself is not a health hazard, but does slightly weaken the
wares, and provides admission for moisture into the claybody if it is
porous. In the case of glass or glaze pooled in the bottom of a bowl, the
divisions between the cracks are usually much broader than the normal craze
pattern, and there is the chance of chunks of glass being released into
food, thus a bowl with significant glaze or glass melted in the bottom is
not a functional form.
This has come up again and again in the past on Clayart. It is always
better to devise stable glazes that do not craze, but people have been
eating off of crazed dishes and storing foods in crazed pots for millennia,
with absolutely no evidence of any negative health effects. Putting glass i=
n
the bottom of bowls is a whole different case, because of the danger of
chunks of glass.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
fran johnson on sat 14 aug 10
On 8/13/10 8:19 PM, "Randy McCall" wrote:
> Is there anything I need to know before I melt some glass in the bottom o=
=3D
f
> some bowls at Cone 6?
> Just asking before I try it.
> Randy
At the local high school where I worked with the art teacher the students o=
=3D
ften would imbed marbles and pieces of stained glass into the clay. For the=
=3D
most part they were successful. They fired at cone 6, bisque at 05.,=3DA0T=
he=3D
clay cracked a bit around the glass, but usually not enough to make to des=
=3D
troy the pot. The glass would melt and run down the sides of the bowl, reac=
=3D
ting with the glaze. Got some interesting results.=3D20
=3DA0
Some would cut holes in the walls and imbed the glass so it would melt insi=
=3D
de and out. Most of the time the openings were part of the design.
=3DA0
One of the students made a glaze incorporating small bits of broken glass. =
=3D
Nice results, but hard on the hands.
=3DA0
Fran
Alice DeLisle on sat 14 aug 10
Randy asked:
"Is there anything I need to know before I melt some glass in the bottom of=
some
bowls at Cone 6?"
I have been making ceramic tiles with glass on them and firing to cone 5-6.=
I
make wells in the tops of the clay tiles before bisque firing. Then I put
marbles, glass gems (the things they use in flower arranging), or pieces of
stained glass in them during the glaze firing. Sometimes there is glaze un=
der
the glass and sometimes I glaze around the wells. The results are some ver=
y
pretty, geode-looking effects. Most of the glass has lots of cracks in it =
after
firing but it is stable and does not fall off of the tiles. Definitely not=
a
surface for food, though. Sometimes the melting glass displaces the colors=
in
the surrounding glaze (chromatography), giving some beautiful halos of colo=
r,
depending on the colorants in the glaze. I am still experimenting with the
colors - both of the glass and the glaze. If you would like to see photos,=
I
can email them directly. I had a table with a 12 x 12 in tile in the top a=
t a
craft fair recently and if I had a dollar for every time a person stopped a=
nd
touched the tile I would be rich! And kids loved it.
I bought one stained glass at a glass store and the store owner warned me t=
hat
the glass was outside of the recommended coefficient of expansion range for
slumped glass. Interestingly, it doesn't crack the way the other glass doe=
s but
is much smoother.
Alice DeLisle
wanderland@att.net
http://delisle.aftosawebhosting.com
http://www.etsy.com/shop/IslandTextures
Doug Trott on tue 17 aug 10
Keep in mind that the colorants used in glass are basically the same that w=
e
use in glazes, and may not be food-safe. Glassblowers are usually careful
to make sure vessels for food or drink are lined with clear glass.
You can purchase glass with varying coefficients of expansion, and could
produce different results, particularly on your cooling process. Glass
objects need to be tempered to reduce stress, which, depending on thickness=
,
involves a slow cooling process often of at least a day. I think that
cooling has to be particularly slow around 900 deg F - I don't recall the
exact temperature.
Doug
On Fri, Aug 13, 2010 at 7:19 PM, Randy McCall wrote:
> Is there anything I need to know before I melt some glass in the bottom o=
f
> some bowls at Cone 6?
>
> Just asking before I try it.
>
> Randy
>
>
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