william schran on sat 31 jan 04
Shwn wrote:> I want to insure that I get up to temp. to melt
the glaze but I'm unsure how determine this. I usually look at the piece during
raku to see if the glaze has matured, and how much temperature difference
will there be inside and outside of the saggar. If only I had a pyrometer!!<
How about a small pot or draw ring with the glaze applied that you
set on top of the sagger and when you see that glaze melted to your
satisfaction, wait a short bit longer, then pull the sagger or shut
off kiln.
Bill
Shawn McGuire on sat 31 jan 04
Hi Folks-
I was wondering if anyone could offer some advice on saggar firing in a
raku kiln, I've never done this before. My idea is this. I would like to try to
achieve a nice low-fire, copper-red reduction glaze. I'm placing my piece in a
large saggar, then into an old electric kiln that I've converted to a raku
kiln. The glaze I'm using is a basic Gerstly/Neph. raku base, some Red Copper
Oxide I just got my hands on, and a wee bit of Rutile. I'm stilting the piece,
and keeping it from coming into contact with the combustibles (sawdust and
hardwood chunks) in the saggar. I want to insure that I get up to temp. to melt
the glaze but I'm unsure how determine this. I usually look at the piece during
raku to see if the glaze has matured, and how much temperature difference
will there be inside and outside of the saggar. If only I had a pyrometer!!
Guess I'll just fire the crap out of that sucker and see how it goes. If anyone
has tried something similar I would love some suggestions, if not I'll let you
know how it goes. Thanks.
over-and-out,
~S~
Ababi on sun 1 feb 04
Hello Shawn
I do not want to break you heart- but you did not invent the wheel.
If you can get one of the old Claytimes from 1998 I think- there is an article by Charlie
Ridges ( sorry for misspelling)
Perhaps him or Linda might help you.
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://ababi.active.co.il
http://www.matrix2000.co.nz/Matrix%20Demo/Ababi.htm
A link to the ceramics forum in Hebrew: (You must have Hebrew fonts)
http://www.botzpottery.co.il/kishurim.html
---------- Original Message ----------
> Hi Folks-
> I was wondering if anyone could offer some advice on saggar firing in a
>raku kiln, I've never done this before. My idea is this. I would like to try to
>achieve a nice low-fire, copper-red reduction glaze. I'm placing my piece in a
>large saggar, then into an old electric kiln that I've converted to a raku
>kiln. The glaze I'm using is a basic Gerstly/Neph. raku base, some Red Copper
>Oxide I just got my hands on, and a wee bit of Rutile. I'm stilting the piece,
>and keeping it from coming into contact with the combustibles (sawdust and
>hardwood chunks) in the saggar. I want to insure that I get up to temp. to melt
>the glaze but I'm unsure how determine this. I usually look at the piece during
>raku to see if the glaze has matured, and how much temperature difference
>will there be inside and outside of the saggar. If only I had a pyrometer!!
>Guess I'll just fire the crap out of that sucker and see how it goes. If anyone
>has tried something similar I would love some suggestions, if not I'll let you
>know how it goes. Thanks.
>over-and-out,
>~S~
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Shawn McGuire on sun 1 feb 04
Good suggestion Bill, and kinda what I was thinking. My concern is that the
temp. is going to be dramatically different inside/outside the saggar. Like I
mentioned before it's a LARGE saggar (50 lbs of Laguna #200 raku clay) and
thickly thrown as a bottomless, topless cylinder and I'm using two round kiln
shelves as top/bottom. It will be interesting to see how both the mass of the
cylinder and the refractory properties of the shelves will effect the atmosphere
inside the sagger. Will also be interested to see how the kiln breaths with
almost the entire firing chamber taken up by the mass of the saggar, as there are
only a couple inches left on the sides and top for air flow. This is my only
means by which to fire in total reduction so I'm excited to see if it works
out.
On another note, has anyone used this Red Copper Oxide before? Last night I
dry mixed all my ingredients, and when I added water all the copper separated
and floated to the top. I finally got it into suspension with some dish
detergent, but was wondering if anyone knew what the advantage of using this stuff
is as opposed to just regular Black Copper Oxide. I read that it's "reduced"
form of Copper Oxide but I'm unclear what this means I guess. Thanks.
over-and-out
~S~
Riggs on sun 1 feb 04
Ababi wrote:
Hello Shawn
"I do not want to break you heart- but you did not invent the wheel.
If you can get one of the old Claytimes from 1998 I think- there is an article by Charlie
Rigg. Perhaps him or Linda might help you."
-----------------------------------------------------------------------------------
Thanks Ababi for mentioning our Saggar Firing in a Raku Kiln technique.
I think what Shawn is trying to achieve is very different from what we
do. He is wanting to achieve a reduction red on a copper glaze whereas
our goal is to fume the terrasiged and polished surface of a pot with
copper and salt and sawdust.
My suggestion to Shawn is that he invest in a pyrometer if he is serious
about achieving repeatable results from a saggar firing where he can't
see the glaze. Then start testing the process with test pieces inside
a saggar until he reaches a temperature where the glaze melts inside the
saggar. If the saggar containers are fairly uniform in claybody type
and thickness then he should have a good idea that he'll get repeatable
results at that temperature.
I know a lot of people don't use pyrometers when firing raku.
Personally, even if I can see the glaze melt, I have much more control
of the outcome of firings if I use a pyrometer--so that I have an idea
when it's time to check the glaze melt. With naked raku where one is
using a slip covered with a glaze the pyrometer is like a signal to
start checking the melt stage so that the glaze doesn't get beyond the
orange peel stage and comes off the pot without any problem.
Hope this helps.
Linda
>
>
>
Shawn McGuire on tue 3 feb 04
Thanks Linda. I am seriously considering a pyrometer and I am sure it will
be money well spent. Just did some Raku yesterday and underfired every piece!!
Frustrating is an understatement. I was using partial tanks of propane and I
think they were freezing up a bit on me. I guess it's just another lesson
learned. Thanks again for the advice.
over-and-out
~S~
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