Eric Suchman on thu 23 may 02
How low a temperature is salt and or sodium active? Can I use salt either
as a spary on the clay or in a cup next to ware in a terra cotta firing?
Say ^04, and expect any results? I know I should just try it but I'm
kilnless at the moment and am doing cerebral ceramic excersizes at this
point in time....
Jeff Tsai on thu 23 may 02
Eric wrote:
"How low a temperature is salt and or sodium active? Can I use salt either
as a spary on the clay or in a cup next to ware in a terra cotta firing?
Say ^04, and expect any results? "
Eric, You can expect reaction from sodium at cone 04 definitely. Even as low
as cone 020, sodium will begin to react, though at that temperature, not
quite as much. I've seen good results around 010 to 01.
Putting the sodium in a cup next to the piece is one way. Laying sodium
around the piece is another. I would avoid, but perhaps experiment with one
piece, putting a sodium solution on the clay itself as the sodium will react
with the clay and could, in large amounts, melt the clay. This may no melt
the pot, but it could cause cracking and I've seen sodium leach out of clays
months after firings because too much sodium soaked into the piece during
the
firing.
Generally, avoid direct contact between the sodium and the clay piece. That
is a huge generalization though. I don't usually do it cause I like the
little white marks the sodium leaves, but I also have more breakage than
most
people firing at low fire salt temperatures.
-jeff
iandol on fri 24 may 02
Dear Eric Suchman,
Sodium Chloride melts at 803 Celsius and Sodium Carbonate at 851 =
Celsius, so these are the lowest temperatures at which anything will =
happen. But until the temperature is take to somewhere over 1100 Celsius =
they do not undergo chemical reactions with the compounds in clay. So =
with clay fired at Cone 04 you would expect both to leach out if the =
clay became wet.
Common salt does not vapourise to any marked extent at ^04, nor does Na =
Carb decompose unless in contact with free silica or mature porcelain in =
this range so you could predict for yourself what the results might be. =
I will be take to task if I try to influence your into believing that =
common salt reacts with K-Felspar or that Na carb does not instantly =
decompose when it is taken to red heat....
Hope you get your kiln back on line.
Best regards,
Ivor Lewis.
Steve Mills on fri 24 may 02
Eric,
The latter idea will only work in a fuel burning kiln; salt volatilises
at a comparatively low temperature and in a fuel Kiln will settle on the
wares *downwind* of it: it and the silica in the clay forming a glaze
when a temperature high enough to combine them is achieved. Whether or
not this will work at 04 would, I think, depend on how low firing the
clay is. Fremington Clay from north Devon in the UK would probably work
as it is vitreous at about that point, and makes an excellent slip glaze
at stoneware temperatures. As a technique, putting pots of salt in a
fuel fired stoneware Kiln works very well, I know, as it is used
historically in Kilns in several European countries, especially France
where I learnt it. It is the technique we use in our wood fired kilns to
excellent effect, and it saves an awful lot of effort, not to mention
the lack of clouds of white *smoke* which accompanies a conventional
salt firing at the salting point.
Steve
Bath
UK
In message , Eric Suchman writes
>How low a temperature is salt and or sodium active? Can I use salt eithe=
>r
>as a spary on the clay or in a cup next to ware in a terra cotta firing?
>Say ^04, and expect any results? I know I should just try it but I'm
>kilnless at the moment and am doing cerebral ceramic excersizes at this
>point in time....
--
Steve Mills
Bath
UK
Sue Clery on fri 24 may 02
I have used salt directly on pieces in pit fires. I have not experienced
any breaking, or long-term leaching problems. And, the effects have been
great. I don't know what temperature these fires have gotten to though. I
have used Standard's white stoneware for these pit fires.
Have fun!
Sue
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
Behalf Of Jeff Tsai
Sent: Thursday, May 23, 2002 7:58 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: low fire salt/sodium
Eric wrote:
"How low a temperature is salt and or sodium active? Can I use salt either
as a spary on the clay or in a cup next to ware in a terra cotta firing?
Say ^04, and expect any results? "
Eric, You can expect reaction from sodium at cone 04 definitely. Even as low
as cone 020, sodium will begin to react, though at that temperature, not
quite as much. I've seen good results around 010 to 01.
Putting the sodium in a cup next to the piece is one way. Laying sodium
around the piece is another. I would avoid, but perhaps experiment with one
piece, putting a sodium solution on the clay itself as the sodium will react
with the clay and could, in large amounts, melt the clay. This may no melt
the pot, but it could cause cracking and I've seen sodium leach out of clays
months after firings because too much sodium soaked into the piece during
the
firing.
Generally, avoid direct contact between the sodium and the clay piece. That
is a huge generalization though. I don't usually do it cause I like the
little white marks the sodium leaves, but I also have more breakage than
most
people firing at low fire salt temperatures.
-jeff
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