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pyrometers and raku?

updated fri 6 feb 04

 

Susan Giddings on tue 3 feb 04


Hello,


I don't understand why people don't seem to use cones with Raku firing. I've done Raku with and without pyrometers, with and without cones, and with and without both. I think the ideal is to have both, but if I had to choose one over the other, I think I'd rather have cones. There are enough instances where pyrometers are not accurate and they have no way of measuring "heat work", just absolute temperature. I think cones are a better guide to glaze melt. Yes, you can just look in at the glazes and see how they are melting. Raku is not so hot that seeing into the kiln is as problematic as it is at higher stoneware temperatures. But, personally, I'd rather see a cone melt just to be sure. And cones are so inexpensive.


I was going to post this as an answer to questions asked about the need for pyrometers in Raku kilns and was surprised that others hadn't already mentioned it. And then it occured to me that there are people in the group I sometimes fire with that never use cones in Raku. They would rather go by pyrometer.  I don't understand. Is there some reason why people choose to avoid using cones in Raku firings?


S


------------------
Susan Giddings
"There are painters who transform the sun into a yellow spot, but there are others who, thanks to their art and intelligence, transform a yellow spot into the sun." — Pablo Picasso



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Simona Drentea on wed 4 feb 04


In a message dated 02/03/2004 8:14:43 PM Mountain Standard Time,
coneten@HOTMAIL.COM writes:
<there some reason why people choose to avoid using cones in Raku firings? >>
Several of the old raku books I've been reading (even from the 80's & early
90's) have said that cones are useless for raku. I've been wondering about why
that is, since in the class I just took, we did use cones. The instructor
said she could tell by eyeballing the glaze too when pieces should be pulled,
but she did use the cones as well.

Unfortunately, the books are back at the library, so I don't know what if any
explanation they gave. It wasn't just one book though, I read this (or saw it
on video) multiple times.

Simona in snowy Colorado

Marcia Selsor on wed 4 feb 04


Susan,
I use a pyrometer rather than just watching the glaze melt because I use
a lot of matt raku glazes. I fire fast and believe a cone would not have
enough "heat work" time to accurately melt when the raku glaze is melting.
Just my thought,
Marcia

Susan Giddings wrote:

> Hello,
>
> I don't understand why people don't seem to use cones with Raku firing.
> I've done Raku with and without pyrometers, with and without cones, and
> with and without both. I think the ideal is to have both, but if I had
> to choose one over the other, I think I'd rather have cones. There are
> enough instances where pyrometers are not accurate and they have no way
> of measuring "heat work", just absolute temperature. I think cones are a
> better guide to glaze melt. Yes, you can just look in at the glazes and
> see how they are melting. Raku is not so hot that seeing into the kiln
> is as problematic as it is at higher stoneware temperatures. But,
> personally, I'd rather see a cone melt just to be sure. And cones are so
> inexpensive.
>
> I was going to post this as an answer to questions asked about the need
> for pyrometers in Raku kilns and was surprised that others hadn't
> already mentioned it. And then it occured to me that there are people in
> the group I sometimes fire with that never use cones in Raku. They would
> rather go by pyrometer. I don't understand. Is there some reason why
> people choose to avoid using cones in Raku firings?

Pamela Watkins on wed 4 feb 04


Susan Giddings wrote:
clip
>There are enough instances where pyrometers are not accurate and they have no way of measuring "heat work", just absolute temperature. I think cones are a better guide to glaze melt. Yes, you can just look in at the glazes and see how they are melting. Raku is not so hot that seeing into the kiln is as problematic as it is at higher stoneware temperatures. But, personally, I'd rather see a cone melt just to be sure. And cones are so inexpensive.
**Hi Susan,

Although there is no "rule" that cones cannot be used, in a reduction atmosphere with multiple firings they are impractical and are much less accurate than a pyrometer. Instructors use them in an aid to teaching the rate of fire and the look of the glaze melt. I'm not sure what you mean by the difference in "heat work" and absolute temperature.

The majority of Raku-ers chose not to use cones or a pyrometer and have become familiar with the process, look of the glaze melt, and use a bit intuition- Intuition complements the history, spontenaity and artistic attachment
to the whole process.

As Steven Branfman says in his book Raku, A Practical Approach , "The only cones that should be used near a raku kiln are ice cream cones~Unless you are glazing with a matt or working for smoke effects where the melt could not be witnessed, and then a pyrometer is recommended." I highly recommend this book if you are firing Raku. It has been a great reference as I am just about to complete construction of a recycled Raku kiln.

Peace,
Pamela
~jaq









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Craig Dunn Clark on wed 4 feb 04


Simona, I don't see why a cone would not work. However, if you are
looking into the kiln to pay attention to what the cone is doing then you
may just as easily look at the melt of the glazes on the pots. Once you have
done it enough times the color of the kiln atmosphere is also a very good
indicator as to when to pull the pots.
As to the use of pytometers..they are also an easy way to know where you
are in the firing. As Marcia pointed out they are of particular use if you
are doing copper matts. If you are using standard crackle glazes just look
for a reflection on the pots. That's when its time to pull them.
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org

----- Original Message -----
From: "Simona Drentea"
To:
Sent: Wednesday, February 04, 2004 1:21 AM
Subject: Re: Pyrometers and Raku?


> In a message dated 02/03/2004 8:14:43 PM Mountain Standard Time,
> coneten@HOTMAIL.COM writes:
> <Is
> there some reason why people choose to avoid using cones in Raku firings?
>>
> Several of the old raku books I've been reading (even from the 80's &
early
> 90's) have said that cones are useless for raku. I've been wondering
about why
> that is, since in the class I just took, we did use cones. The instructor
> said she could tell by eyeballing the glaze too when pieces should be
pulled,
> but she did use the cones as well.
>
> Unfortunately, the books are back at the library, so I don't know what if
any
> explanation they gave. It wasn't just one book though, I read this (or saw
it
> on video) multiple times.
>
> Simona in snowy Colorado
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.

Christy Pines on wed 4 feb 04


I don't own a pyrometer, so don't really know how it works (assuming it's like a thermometer - measuring heat/temperature). I do own a raku kiln - cranked it up last weekend in the 20 degrees of Connecticut winter, and had trouble with my glazes not being fully melted.

What is the "reading" you look for on your pyrometer to be sure that you are stopping at the right point?

christy, in connecticut, wanting to do another raku firing this weekend, but not wanting to ruin more pots.

-----Original Message-----
From: Marcia Selsor
Sent: Feb 4, 2004 8:10 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Pyrometers and Raku?

Susan,
I use a pyrometer rather than just watching the glaze melt because I use
a lot of matt raku glazes. I fire fast and believe a cone would not have
enough "heat work" time to accurately melt when the raku glaze is melting.
Just my thought,
Marcia

william schran on thu 5 feb 04


Susan wrote:>I don't understand why people don't seem to use cones
with Raku firing.... There are enough instances where pyrometers are
not accurate and they have no way of measuring "heat work", just
absolute temperature..... Is there some reason why people choose to
avoid using cones in Raku firings?<

Yes, you're correct, cones measure "heat work", but they are only
accurate if the temperature rise is a specific amount of rise over a
specific amount of time. The cones will bend at a higher or lower
temperature if the temperature rises faster or slower than the
specifications written by the manufacturer. In this instance, when a
firing takes less than an hour, I would think a pyrometer might
provide a better device for judging temperature.

This is all just my opinion, because I have never used either one for
my raku firings - I just look at the glaze melt on the pots. When we
get cranking during our summer raku class, we've had firings towards
the end of the night down to 15 minutes!

Bill