freewill on wed 5 nov 97
So, uh......how do you you tell wether a problem is being caused by the
chemical formulation of the glaze or by the firing schedule?
(I suppose you're going to tell me that I should feed the glaze through my
glaze software and chart every gauge on my oxyprobe. I was hoping for a
more "primitive" answer. )
thanks
jenni
Karl P. Platt on wed 5 nov 97
Jenni,
Well, um, the answer depends on a couple of things -- all of which are not
oxyprobe readings. In fact, I'll submit that the device is of dubious
value -- and real expensive. This, however, is another topic entirely.
I'll just say that I'm real partial to metering orifices -- which are
cheap, real accurate, don't need batteries and don't change with time.
If the glaze is underfired it'll likely be crusty and dry. If it's
overfired, there'll be symptoms of this elsewhere, too. Such as in the
color of the body.
Having an idea of what goes into the glaze will help determine whether
it's been developed to accomodate the temperatures at which you fire. You
can do this manually or you can use a PC/Mac/etc.
KPP
Craig Martell on wed 5 nov 97
At 10:34 AM 11/5/97 EST, Jenni wrote:
>----------------------------Original message----------------------------
>
>So, uh......how do you you tell wether a problem is being caused by the
>chemical formulation of the glaze or by the firing schedule?
Hello Jenni:
If your firing schedule is fairly conformant with generally accepted rates
of temp. rise, reduction-oxidation schedules etc., and your firing schedule
has, and is producing good results you probably don't want to mess with the
firing.
If you are firing glazes, slips, and clays that are not responding favorably
to that schedule, and you wish to use these materials, you are then faced
with changing them to mesh with your firing practices.
So, I guess my answer is that if your firing schedule is producing good
results, it shouldn't be suspected of culpability. If nothing in the kiln
is coming out right, then change the firing practices and leave the glazes
alone. There is an incredible amount of information on kilns, firing, and
ceramic chemistry available to us and will help sort stuff like this out.
hoping that I made sense, Craig Martell-Oregon
Craig Martell on thu 6 nov 97
At 06:42 PM 11/5/97 EST, Karl Platt wrote:
>----------------------------Original message----------------------------
>
>Jenni,
>
>Well, um, the answer depends on a couple of things -- all of which are not
>oxyprobe readings. In fact, I'll submit that the device is of dubious
>value -- and real expensive.
Karl:
Well, I guess that you can submit whatever you like but I think that those
of us who use oxyprobes will probably take issue with your submission. It's
better to have some sort of quantitative reading of kiln atmosphere, even if
it's only at one point, than none at all. It's hard to find neutral, which
gives the most efficient temp. rise with your eyes and nose. It's also real
difficult to assess the amount of reduction or oxidation in the kiln and an
oxyprobe aids this process greatly. I've used an AIC oxyprobe for about 6
yrs with very good results. I use less propane than before and the glazes,
especially copper reds and celedons are much better. I paid $600 bucks for
the oxyprobe and it has paid for itself many times over.
regards, Craig Martell-Oregon
KLeSueur on sat 15 nov 97
I use a Bacarach CO2 analyzer and wouldn't fire without it. It's just one more
tool in the arsenal for reduction firing. Looking at the flame is just not
accurate enough......at least not with my glazes. A 9.5 reduction flame looks
the same as a 10....... but the finished glaze looks very different.
The assembly costs about $150. A quartz sampling tube is necessary but
shouldn't be bought from the supplier. Any good lab supply can get the tubing
for about $3.00.
Kathi LeSueur
| |
|
