dianamp@COMCAST.NET on tue 16 nov 10
Hi Clayart:
We are new to soda firing. Have done two in the new kiln so far.
I notice that some recipes add Borax to the glaze mixture,
which is a combination of sodium carbonate and sodium bicarbonate.
Can someone who has tried the mixture both with and without
Borax comment on the difference I might expect if I add some
Borax??? I realize that it is an active low temp flux.
Thanks again for your help.
Sincerely,
Vince Pitelka on tue 16 nov 10
Diana Pancioli wrote:
"We are new to soda firing. Have done two in the new kiln so far. I =3D
notice that some recipes add Borax to the glaze mixture, which is a =3D
combination of sodium carbonate and sodium bicarbonate. Can someone who =3D
has tried the mixture both with and without Borax comment on the =3D
difference I might expect if I add some Borax??? I realize that it is an =
=3D
active low temp flux."
Hi Diana -=3D20
As you point out, Borax is a very powerful low-temperature flux, and any =
=3D
addition of a powerful flux produces a weaker glass - more flux, less =3D
silica. It makes the soda deposition on the surface more fluid, and you =
=3D
get less orange-peel effect, and in the fired piece you get more crazing =
=3D
and a less-durable glaze. Personally, I don't understand the logic =3D
behind adding borax, because it tends to diminish the results my =3D
students and I like the most. I should point out that I am certainly no =
=3D
expert on using Borax in soda mixtures, precisely for the reasons =3D
mentioned above. I do not care for the results I have seen, so I have =3D
seen no reason to use it. I will be very interested in hearing from =3D
others who do use Borax in their mix. =3D20
I would also worry about the effect on the kiln, since you are firing an =
=3D
IFB soda kiln. A mix with Borax will likely attack the IFB even faster =3D
than a straight soda mixture. =3D20
I am curious why you are using a mix of carbonate and bicarbonate. I =3D
was under the impression that the combination is beneficial only when =3D
charging with burritos, which is also much harder on the kiln. But =3D
again, I look forward to hearing other opinions on this.
- Vince=3D20
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu=3D20
http://iweb.tntech.edu/wpitelka
Dan Hill on wed 17 nov 10
Diana Wrote
We are new to soda firing. Have done two in the new kiln so far.
I notice that some recipes add Borax to the glaze mixture,
which is a combination of sodium carbonate and sodium bicarbonate.
Can someone who has tried the mixture both with and without
Borax comment on the difference I might expect if I add some
Borax??? I realize that it is an active low temp flux.
Diana
I am sure I tried the soda mix without the borax at some point but have not
in recent memory. The theory I believe is that the addition of borax will
smooth out the surface from the soda build up, less pebbly, I also think
that it helps to melt the soda glaze and prevent a rough surface when doin=
g
soda firing at ^6.
How have the firings gone so far? Try your Chocolate and the Iron Red in th=
e
soda. I have had some interesting results with those.
Dan Hill
Hill Pottery
^6 soda fired Porc. and Stoneware
Vince Pitelka on wed 17 nov 10
Regarding the use of Borax in the soda mix for soda firing, Dan Hill =3D
said:
"I am sure I tried the soda mix without the borax at some point but have =
=3D
not in recent memory. The theory I believe is that the addition of borax =
=3D
will smooth out the surface from the soda build up, less pebbly, I also =3D
think that it helps to melt the soda glaze and prevent a rough surface =3D
when doing soda firing at ^6."
Hi Dan -=3D20
That's certainly true about the addition of Borax producing a smoother =3D
surface, because the same strategy is used to make salt firing viable at =
=3D
lower temperatures. I still worry about the degree to which it makes =3D
the glaze surface weaker, and increases crazing. Regarding rough =3D
surfaces, my work has all been soda fired to cone-6 for the past eight =3D
years or so, using just soda ash in water solution, and I have not =3D
noticed any tendency towards rough surfaces. I like a bit of pebbling - =
=3D
it's part of why I soda fire. I tend to do a very light soda firing =3D
that also emphasizes flashing of the clay. To see some examples, go to =3D
http://www.accessceramics.org/results/artist/186/
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu=3D20
http://iweb.tntech.edu/wpitelka
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