Pat Lindemann on wed 9 may 07
So I experimented a bit with my last glaze fire, and put 3 small bisque
dishes of soda ash in the kiln, one on each level. I have a gas updraft.
The top two levels of the kiln had a beautiful light sheen but on the bottom
level, where it appears the hottest, judging from the cones, the dish had
been eaten thru, it looked like. The dish had a hole in it, and there was a
green glass 'spilled' underneath the dish. Upon closer inspection, the
thickness of the dish appeared to have thinned considerably. My question
is- is soda ash so corrosive that it would 'eat thru' the inside of a clay
dish?
thanks!
Pat
Hank Murrow on wed 9 may 07
On May 9, 2007, at 8:36 AM, Pat Lindemann wrote:
> So I experimented a bit with my last glaze fire, and put 3 small
> bisque
> dishes of soda ash in the kiln, one on each level. I have a gas
> updraft.
> The top two levels of the kiln had a beautiful light sheen but on
> the bottom
> level, where it appears the hottest, judging from the cones, the
> dish had
> been eaten thru, it looked like. The dish had a hole in it, and
> there was a
> green glass 'spilled' underneath the dish. Upon closer inspection,
> the
> thickness of the dish appeared to have thinned considerably. My
> question
> is- is soda ash so corrosive that it would 'eat thru' the inside of
> a clay
> dish?
Yes Pat. The way to avoid this is to fire the dishes holding the soda
to cone 10 first. Then the soda will not get into the pores of the
body as it has been vitrified.
Cheers, Hank
www.murrow.biz/hank
Lee Love on thu 10 may 07
On 5/10/07, Pat Lindemann wrote:
> thickness of the dish appeared to have thinned considerably. My question
> is- is soda ash so corrosive that it would 'eat thru' the inside of a clay
> dish?
Put your soda in a glaze fired dish. Another way to do it, is put
it in a sea shell and put the shell on a glazed dish. I would also
wad the dish.
My friend Genvieve has been putting soda in a test tube shaped
container. She says it peculates and disperses better. It is a
tube that is glazed inside and glaze fired first.
You could also try the dip, but make sure you wad the pots. I
think the dip effects the kiln furniture less.
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://mashikopots.blogspot.com/
"To affect the quality of the day, that is the highest of arts." -
Henry David Thoreau
"Let the beauty we love be what we do." - Rumi
Vince Pitelka on thu 10 may 07
Ivor Lewis wrote:
"I do not believe the established custom of assuming these salts are highly
volatile or that they decompose when heated or react with water vapour to
release Sodium Oxide which reacts with clay.
Much better to inject a hot solution of soda or use the process devised by
Gail Nichols."
Ivor -
Ah, there you go again. When it comes to salt-firing, it IS the established
custom, for the simple reason that it works best. Moistened rock salt can
be dumped into the firebox, or moistened "burritos" of rock salt wrapped in
newspaper can be dropped into the firebox. In either case, the moisture
turning to steam helps the salt to dissociate and disseminate
instantaneously, and the effect is easily discernable by the clouds of fumes
emmanating from every opening in the kiln, and by the almost immediate
effect visible on draw rings.
The process that Gail Nichols uses is excellent for getting the spectacular
effects that she seeks and achieves, but not for the much more light-handed
soda effect I seek at cone 6 on my patterned colored clay work
(http://iweb.tntech.edu/wpitelka/). For that, the hot saturated aqueous
solution of soda ash sprayed into the firebox is far more effective.
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Carole Fox on thu 10 may 07
On Thu, 10 May 2007 08:37:04 +0900, Lee Love wrote:
> My friend Genvieve has been putting soda in a test tube shaped
>container. She says it peculates and disperses better.
Lee - what does "peculate" mean in this context? Webster gives a synonym
of "embezzle", which doesn't seem to fit this usage.
Always seeking to learn -
Carole Fox
Dayton, OH
gsomdahl on thu 10 may 07
My guess is that the soda melts before it vaporizes. The liquid soda
soaks into the bisqued clay and dissolves it.
One simple way to add soda to a kiln that is not build with access ports
is to make small cups (tablespoon size) out of wadding. Let these dry 24
hrs and check that they have no cracks. Fill with soda and set
throughout the kiln. Placing more in lower areas should increase the
concentration there.
Pat Lindemann wrote:
> My question is- is soda ash so corrosive that it would 'eat thru' the
> inside of a clay dish?
>
--
This is a post only account. Send replies to "gene" at my ".com" domain named "somdahl".
Ivor and Olive Lewis on thu 10 may 07
Dear Pat Lindemann,
I suppose this is predictable outcome. You have borrowed a technique =
from the annals of Salt Glazing which can give the same effects if there =
is more than a small amount of sodium chloride in the containers.
Years ago when I did some saggar firing I constructed small shelves =
inside the saggars to hold about a teaspoon of salt, then fired up to =
cone 8. The results were moderately catastrophic as my clay utensil was =
locally dissolved by molten salt.
Sodium Carbonate behaves in a similar fashion. As a molten salt it is =
used to dissolve silicate samples for analysis, making them soluble in =
water or dilute acids.
I do not believe the established custom of assuming these salts are =
highly volatile or that they decompose when heated or react with water =
vapour to release Sodium Oxide which reacts with clay.=20
Much better to inject a hot solution of soda or use the process devised =
by Gail Nichols.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Rudy Tucker on fri 11 may 07
gsomdahl,
Do you have any reason, experience perhaps, to believe that liquid soda
would not soak into unfired cups made from the wadding material? I think
that this approach would result in the same or even less desirable results
as using bisque fired cups. After all, the green wadding will be very porous
also and possibly more reactive with the molten sodium. I would not try this
method without the back up of a stoneware fired dish under the wadding cup.
Rudy Tucker
----- Original Message -----
From: "gsomdahl"
To:
Sent: Thursday, May 10, 2007 10:24 AM
Subject: Re: Soda Glazing
> My guess is that the soda melts before it vaporizes. The liquid soda
> soaks into the bisqued clay and dissolves it.
>
> One simple way to add soda to a kiln that is not build with access ports
> is to make small cups (tablespoon size) out of wadding. Let these dry 24
> hrs and check that they have no cracks. Fill with soda and set
> throughout the kiln. Placing more in lower areas should increase the
> concentration there.
Lee Love on fri 11 may 07
On 5/11/07, Carole Fox wrote:
>
>
>
> > My friend Genvieve has been putting soda in a test tube shaped
> >container. She says it peculates and disperses better.
>
> Lee - what does "peculate" mean in this context? Webster gives a synonym
> of "embezzle", which doesn't seem to fit this usage.
Please take a good guess Carole Fox in Dayton, OH Context is everything....
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://mashikopots.blogspot.com/
"To affect the quality of the day, that is the highest of arts." -
Henry David Thoreau
"Let the beauty we love be what we do." - Rumi
Ivor and Olive Lewis on fri 11 may 07
Dear Lee Love
You say "Genvieve has been putting soda in a test tube shaped =
container. She says it peculates and disperses better. It is a tube that =
is glazed inside and glaze fired first."
"Peculates" Do she really mean Embezzle ?
Sodium chloride, especially the larger crystalline variety =
"Decrepitates". But it seem doubtful that this would happen to a fine =
powder.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
gsomdahl on sat 12 may 07
This is a common practice with soda and salt firings in Minnesota. No
problem with the cups unless they are cracked or get dipped over.
Gene
Rudy Tucker wrote:
> gsomdahl,
>
> Do you have any reason, experience perhaps, to believe that liquid soda
> would not soak into unfired cups made from the wadding material? I think
> that this approach would result in the same or even less desirable
> results
> as using bisque fired cups. After all, the green wadding will be very
> porous
> also and possibly more reactive with the molten sodium. I would not
> try this
> method without the back up of a stoneware fired dish under the wadding
> cup.
>
> Rudy Tucker
--
This is a post only account. Send replies to "gene" at my ".com" domain named "somdahl".
Lee Love on sat 12 may 07
On 5/11/07, Rudy Tucker wrote:
> gsomdahl,
>
> Do you have any reason, experience perhaps, to believe that liquid soda
> would not soak into unfired cups made from the wadding material? I think
> that this approach would result in the same or even less desirable results
> as using bisque fired cups. After all, the green wadding will be very porous
> also and possibly more reactive with the molten sodium. I would not try this
> method without the back up of a stoneware fired dish under the wadding cup.
I find glaze fired cups or dishes work the best.
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://mashikopots.blogspot.com/
"To affect the quality of the day, that is the highest of arts." -
Henry David Thoreau
"Let the beauty we love be what we do." - Rumi
Ivor and Olive Lewis on sun 13 may 07
Dear Vince Pitelka,
Thank you for responding=20
I said "I do not believe the established custom of assuming these salts =
are highly
volatile or that they decompose when heated or react with water vapour =
to
release Sodium Oxide which reacts with clay..."
Vince Pitelka responded <salt-firing, it IS the established custom, for the simple reason that it =
works best.>
Vince, there is a table in the first edition of Cullen Parmelee's =
"Ceramic Glazes, page 86, which give the dissociation temperatures of a =
variety of carbonates. C. Parmelee gives the dissociation temperature =
for Sodium carbonate as being above 1750 deg C. I think that was =
published in 1946 and it is well beyond the working temperatures used by =
Potters.=20
"What works best" is not Science.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Ron Roy on mon 14 may 07
Hi Ivor,
Hamer says 860C (1580F) for dissociation of Sodium Carb - bicarbonate comes
apart at 270C.
RR
>Vince, there is a table in the first edition of Cullen Parmelee's "Ceramic
>Glazes, page 86, which give the dissociation temperatures of a variety of
>carbonates. C. Parmelee gives the dissociation temperature for Sodium
>carbonate as being above 1750 deg C. I think that was published in 1946
>and it is well beyond the working temperatures used by Potters.
>
>"What works best" is not Science.
>
>Best regards,
>
>Ivor Lewis.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Vince Pitelka on mon 14 may 07
Ivor Lewis wrote:
"Vince, there is a table in the first edition of Cullen Parmelee's "Ceramic
Glazes, page 86, which give the dissociation temperatures of a variety of
carbonates. C. Parmelee gives the dissociation temperature for Sodium
carbonate as being above 1750 deg C. I think that was published in 1946 and
it is well beyond the working temperatures used by Potters.
"What works best" is not Science."
Ivor -
Actually, it would be better stated "What has been shown to work by
practical experience is more reliable than contradicting science."
When we use carbonates in soda firing, we dissolve them in water and spray
the saturated solution into the kiln, and the sodium is very effeciently
dispersed. It may be that it is never melting, but it is certainly
dispersing effectively.
And regarding salt firing, the boiling point of sodium chloride is 1413 C,
which is around 2500 F. That's higher than cone 10, but we dump the salt
right in the firebox, which is a lot hotter than cone 10.
But here's a good question. Low-fire salt is quite popular. I am
especially fond of Ron Meyers's low-fire salt work on terracotta. So,
what's happenening when we salt a kiln at cone 04? How is the salt
vaporizing and re-depositing on the wares? I'd really like to know the
chemistry of that.
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Lee Love on tue 15 may 07
On 5/15/07, Vince Pitelka wrote:
> But here's a good question. Low-fire salt is quite popular. I am
> especially fond of Ron Meyers's low-fire salt work on terracotta. So,
> what's happenening when we salt a kiln at cone 04? How is the salt
> vaporizing and re-depositing on the wares? I'd really like to know the
> chemistry of
I just read that Meyers works in soda too. (He was the potter judge
for the McKnight I was awarded.) Soda works at low temps. John
Kantar first earthenware to cone 1, where it is vitreous and
introduces soda. You can see his work here:
http://www.handmadepots.com/
I find cone 1 soda intriguing. May work with it this summer
or during my residency in the spring. NCC has a soda kiln. Cone 1
is less expensive to fire at and it makes a vitreous body for
functional work.
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://mashikopots.blogspot.com/
"To affect the quality of the day, that is the highest of arts." -
Henry David Thoreau
"Let the beauty we love be what we do." - Rumi
Ivor and Olive Lewis on tue 15 may 07
Dear Ron Roy,=20
I prefer to trust the values given by Cullen Parmelee, the information =
in CRC handbook and the Tables of Kaye and Laby.
P. J. Durrant describes the elementary properties of Sodium carbonate =
and notes that "Sodium Carbonate looses weight at the rate of about one =
milligram per minute when heated above red heat in a platinum crucible. =
The loss is due partly to decomposition, whereby carbon dioxide is =
expelled leaving a residue of oxide and hydroxide, and partly by =
volatilisation. If sodium carbonate is heated in a porcelain crucible =
considerable loss of weight is observed as silica from the porcelain =
expels carbon dioxide : SiO2 + Na2CO3 =3D Na2SiO3 + CO2
Ivor and Olive Lewis on wed 16 may 07
Dear Lee Love,=20
By now you will have read the quotation form Durrant about the behaviour =
of Sodium Carbonate.
This chemical has been used for decades as a solvent for silicate =
samples that do not respond to other ways of obtaining solutions for =
qualitative analysis. It is known as "The Carbonate Fusion". The =
reaction with Silicon dioxide on fusion above 900 deg C is given as :-
SiO2(s)+Na2CO2(s) =3D> Na2SiO3(s)+CO2(g)
Sodium Silicate is readily soluble in water but can react and =
precipitate SiO2 with an acid.
I tried to look at the McNight site but his photographic images are very =
dark. Disappointing.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Lee Love on fri 18 may 07
On 5/16/07, Ivor and Olive Lewis wrote:
> I tried to look at the McNight site but his photographic images are very dark.
>Disappointing.
I have no clue what you are talking about, but you will have to
turn up your own contrast on your own monitor.
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://mashikopots.blogspot.com/
"To affect the quality of the day, that is the highest of arts." -
Henry David Thoreau
"Let the beauty we love be what we do." - Rumi
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