Nancy Udell on fri 7 jan 05
Hi All, All this talk about cones has gotten me thinking about
something that puzzles me. What is the rationale for the change in
temp from one cone to the next? It appears to be completely random.
Taking for example the numbers from the chart in the back of John
Britt's book (assuming 15 deg per hour ) for self supporting cones.
The increases between cones is set forth below(last column is change
from previous cone). Any thoughts? Have not seen any discussion of
this in all my many books. One interesting thing is that if you take
the numbers from the back of Daniel Rhodes (he has one set and not the
fully detailed chart John has) (1) the numbers are different and (2)
the changes more uniform, although (to me) still not logical. (see
second set of numbers below). Is it that the cones were supposed to do
one thing and actually do another and now that we have better measuring
devices we can see what they are actually doing as opposed to what they
are supposed to do? And even if they were supposed to do Daniel
Rhodes's numbers, what is the logic in not having uniform increases or
uniformly accelerating or decelerating increases?
From John Britt (15 deg per hour self supporting)
014 757 Change
013 807 50
012 843 36
011 857 14
010 891 34
09 907 16
08 922 15
07 962 40
06 981 19
05 1021 40
04 1046 25
03 1071 25
02 1078 7
01 1093 15
1 1109 16
2 1112 3
3 1115 3
4 1141 26
5 1159 18
6 1185 26
7 1201 16
8 1211 10
9 1224 13
10 1251 27
From Daniel Rhodes
012 840 change
011 875 35
010 890 15
09 930 40
08 945 15
07 975 30
06 1005 30
05 1030 25
04 1050 20
03 1080 25
02 1095 15
01 1110 15
1 1125 15
2 1135 10
3 1145 10
4 1165 20
5 1180 15
6 1190 10
7 1210 20
8 1225 15
9 1250 25
10 1260 10
Nancy, in MD where it is raining in the early morning and these are the
things that occupy my mind while i have the first of many cups of
coffee........
Nancy Udell on fri 7 jan 05
Thanks John. Interesting, tho can't say i understand a "mole". I will
check out Daniel Green's book. Am embarking this year on a project of
learning the chemistry of what we do. I have a lot to learn. I love
your book, by the way. It's a very nice job of pulling together all
those recipes that are flying around and its great fun to read and to
look at.
Nancy, in MD where i have now had all the coffee i need and still have
not made a chicken beer butt roaster!
On Jan 8, 2005, at 9:36 AM, John Britt wrote:
> Nancy,
>
> There are others on this list who are better at expaining this but it
> is
> not based on a temerature rationale, but moles of materials like
> alumina,
> silica potassium oxide, calicium oxide, boron, etc. So the moles
> numbers
> have a rationale and then whatever the temperature turnes out to be it
> recorded. You need to read Daniel Green's book,"Handbook of Pottery
> Glazes" (This is the title, I think).
>
> I will also tell you that Orton changes their numbers, which they
> did ....several times since Rhodes but most recently maybe 2 or 3 years
> ago? That is but another reason to not rely on books that are 40 years
> old. There have been advances. In ceramics, for example, there are
> completely different raw materials, bricks and other refractories, kiln
> controllers, etc.
>
> You should, also, definitely go to Orton's website. They are the
> source.
>
> Hope that helps,
>
> John Britt
> www.johnbrittpottery.com
>
John Britt on sat 8 jan 05
Nancy,
There are others on this list who are better at expaining this but it is
not based on a temerature rationale, but moles of materials like alumina,
silica potassium oxide, calicium oxide, boron, etc. So the moles numbers
have a rationale and then whatever the temperature turnes out to be it
recorded. You need to read Daniel Green's book,"Handbook of Pottery
Glazes" (This is the title, I think).
I will also tell you that Orton changes their numbers, which they
did ....several times since Rhodes but most recently maybe 2 or 3 years
ago? That is but another reason to not rely on books that are 40 years
old. There have been advances. In ceramics, for example, there are
completely different raw materials, bricks and other refractories, kiln
controllers, etc.
You should, also, definitely go to Orton's website. They are the source.
Hope that helps,
John Britt
www.johnbrittpottery.com
Hank Murrow on sat 8 jan 05
On Jan 7, 2005, at 4:36 PM, Nancy Udell wrote:
> Hi All, All this talk about cones has gotten me thinking about
> something that puzzles me. What is the rationale for the change in
> temp from one cone to the next? It appears to be completely random.
> Any thoughts? Have not seen any discussion of
> this in all my many books. Is it that the cones were supposed to do
> one thing and actually do another and now that we have better measuring
> devices we can see what they are actually doing as opposed to what they
> are supposed to do?
Dear Nancy;
Pyrometric cones were invented by Hermann Seger to reveal heatwork, and
were constituted by empirical formulae to have even MOLECULAR steps
between cones. While this way of measuring does not permit exactly even
temperature steps between cones, it does reflect accurately how ceramic
materials react to heatwork. This reveals more perfectly the relation
between heatwork and the ceramic materials in the kiln. Here is my
earlier post on the subject:
In David Green's book "Understanding Pottery Glazes", he shows a table
of cones. Here is the table from Cone 5 to Cone 13 in empirical
formulae.
Cone # K2O CaO Al2O3 SiO2
5 .3 .7 .5 5.0
6 .3 .7 .6 6.0
7 .3 .7 .7 7.0
8 .3 .7 .8 8.0
9 .3 .7 .9 9.0
10 .3 .7 1.0 10.0
11 .3 .7 1.2 12.0
12 .3 .7 1.4 14.0
13 .3 .7 1.6 16.0
One may see how elegant the composition of cones is, and how rational
if one is conversant with empirical formulae.
Cheers, Hank in Eugene
www.murrow.biz/hank
| |
|
