Lorraine Pierce on sat 25 jan 03
My first waxwing brown tests from Ron and Jon's book were a very 'foggy' =
uninteresting brown; four hour soak in a kiln coated with ITC. Yesterday =
I opened my ^04 bisque kiln, no ITC coating, no soak, and found the =
refired test tile of waxwing brown looking exactly as pictured in =
Mastering Cone Six Glazes! In the meantime I had ordered a 99% red =
iron oxide from US Pigment,for future testing, thinking my spanish iron =
might be at fault. I still will use it...I am very curious what the =
'double the price' pigment will do. I was told not to alter the amount =
specified in the glaze tho the iron is more pure. testing, testing, =
testing. =20
The first couple that 'saw' my house hope to buy it!! They're potters =
and loved the studio...and everything else. Wow. Came up (north) from =
St. Pete and higher prices! Selling might not be so hard. To potters.=20
Lori Pierce in New Port Richey where it was below 20 degrees in sunny =
Florida outside my door last night.
Ron Roy on sun 26 jan 03
What Lori is describing here is called striking - refiring to a lower
temperature to give crystals the time they need to form - on the way up and
on the way down.
Care must be taken to not fire high enough to remelt the crystals.
If Lori had slow cooled at the right temperature to let the crystals form
in the first firing the second would not be necessary.
Once you find the righ temperature for crystal growth the only limit is the
amount of silica in the surrounding glaze - crystals use up silica as they
grow. Every glaze will act somewhat differently but many will grow crystals
in a similar range - low fire glazes need a lower crystal growing temp for
instance.
Thanks for posting this Lori - important information.
RR
>My first waxwing brown tests from Ron and Jon's book were a very 'foggy'
>uninteresting brown; four hour soak in a kiln coated with ITC. Yesterday I
>opened my ^04 bisque kiln, no ITC coating, no soak, and found the refired
>test tile of waxwing brown looking exactly as pictured in Mastering Cone
>Six Glazes! In the meantime I had ordered a 99% red iron oxide from US
>Pigment,for future testing, thinking my spanish iron might be at fault. I
>still will use it...I am very curious what the 'double the price' pigment
>will do. I was told not to alter the amount specified in the glaze tho the
>iron is more pure. testing, testing, testing.
>
>The first couple that 'saw' my house hope to buy it!! They're potters and
>loved the studio...and everything else. Wow. Came up (north) from St. Pete
>and higher prices! Selling might not be so hard. To potters.
>
>Lori Pierce in New Port Richey where it was below 20 degrees in sunny
>Florida outside my door last night.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Wes Rolley on sun 26 jan 03
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At 12:48 AM 1/26/03 -0500, Ron Roy wrote:
>Once you find the righ temperature for crystal growth the only limit is the
>amount of silica in the surrounding glaze - crystals use up silica as they
>grow.
Ron, do you know of a methodology to predict the temperature at which=20
crystals will be formed for a given set of materials? If such a predictive=
=20
methodolgy were available, it would give a searcher the starting point to=20
use in their testing.
"I find I have a great lot to learn =96 or unlearn. I seem to know far too=
=20
much and this knowledge obscures the really significant facts, but I am=20
getting on." -- Charles Rennie Mackintosh
Wesley C. Rolley
17211 Quail Court
Morgan Hill, CA 95037
wrolley@charter.net
(408)778-3024
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Ron Roy on mon 27 jan 03
Hi Wes,
No - and I don't think anyone can - it is like trying to figuer out
eutectics - all the data is from experimentation.
Putting the glaze in a bisque firing will tell you something - if the
crystals grow then you have a clue - there are so many variables I don't
even think you can apply conclusions form one glaze and apply them to
another even if they have the same end temp.
Probably the best thing is to cool slow during a certain range - making it
long enough - and then just vary the speed to get what you want.
What range would that be? For cone 6 glazes - I'm guessing but from my
dilatometer experiments I know that glazes are pyro plastic for longer than
most of use imagine. Most are still soft at 700C so - 1000C down to 800C
would be my starting point.
If I was working at cone ten I would move the bottom up to 750C and the top
up to 1050C.
All just guesses at this point.
RR
>At 12:48 AM 1/26/03 -0500, Ron Roy wrote:
>
>>Once you find the righ temperature for crystal growth the only limit is th=
e
>>amount of silica in the surrounding glaze - crystals use up silica as they
>>grow.
>
>Ron, do you know of a methodology to predict the temperature at which
>crystals will be formed for a given set of materials? If such a predictive
>methodolgy were available, it would give a searcher the starting point to
>use in their testing.
>
>"I find I have a great lot to learn =96 or unlearn. I seem to know far too
>much and this knowledge obscures the really significant facts, but I am
>getting on." -- Charles Rennie Mackintosh
>
>Wesley C. Rolley
>17211 Quail Court
>Morgan Hill, CA 95037
>wrolley@charter.net
>(408)778-3024
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
=46ax: 613-475-3513=20
Wes Rolley on mon 27 jan 03
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At 07:36 PM 1/27/03 -0500, you wrote:
>What range would that be? For cone 6 glazes - I'm guessing but from my
>dilatometer experiments I know that glazes are pyro plastic for longer than
>most of use imagine. Most are still soft at 700C so - 1000C down to 800C
>would be my starting point.
>
>If I was working at cone ten I would move the bottom up to 750C and the top
>up to 1050C.
Well, this just about brackets it, since I do most work at C 8/9. Your=20
answer was what I expected, I just wanted to confirm from someone who knows=
=20
a lot more than I do.
Wes
"I find I have a great lot to learn =96 or unlearn. I seem to know far too=
=20
much and this knowledge obscures the really significant facts, but I am=20
getting on." -- Charles Rennie Mackintosh
Wesley C. Rolley
17211 Quail Court
Morgan Hill, CA 95037
wrolley@charter.net
(408)778-3024
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