Fran Schwartz on thu 9 feb 06
Dear Clayarters,
A studio-mate of mine here in sunny San Miguel de Allende, Mexico
recently painted a number of pieces in places with RIO and in other places
with Velvet Underglazes.After dipping into a transparent glaze and firing
to cone 05, the RIO had mostly disappeared, but a ghost of gray
remained.The Velvets were fine.
Can you tell us what happened to the missing RIO? And how to keep it from
disappearing?
Everything else here is wonderful.
Thanks for your help. Fran Schwartz
Dannon Rhudy on fri 10 feb 06
It sounds like too thin an application, and, also, if the
piece was dipped after the iron put on - well, you'd be
surprised at how much of the iron can/does drop off in
the glaze container.
Make a richer mixture of the iron, and test it.
regards
Dannon Rhudy
> A studio-mate of mine here in sunny San Miguel de Allende, Mexico
> recently painted a number of pieces in places with RIO and in other places
> with Velvet Underglazes.After dipping into a transparent glaze and firing
> to cone 05, the RIO had mostly disappeared,
---
---
Philip Poburka on fri 10 feb 06
Hi Fran,
If memory serve...
If it was fired in reduction...it would be making 'grey' where, in
oxidation, 'red'
would be.
Might have been too thin an application of RIO also...if mere 'ghosts'
remained...
Phil
Las Vegas
----- Original Message -----
From: "Fran Schwartz"
> Dear Clayarters,
> A studio-mate of mine here in sunny San Miguel de Allende, Mexico
> recently painted a number of pieces in places with RIO and in other places
> with Velvet Underglazes.After dipping into a transparent glaze and firing
> to cone 05, the RIO had mostly disappeared, but a ghost of gray
> remained.The Velvets were fine.
> Can you tell us what happened to the missing RIO? And how to keep it
from
> disappearing?
> Everything else here is wonderful.
> Thanks for your help. Fran Schwartz
>
>
____________________________________________________________________________
__
> 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.
John Britt on fri 10 feb 06
Fran,
I wonder what the name of the glaze was? Leaded or unleaded?
Also, there is a wonderful section in Ian Curie=92s book =93Stoneware Glazes=
=94
where he reprints an article by R. R. Hughan from =93Pottery in Australia=94=
which talks about iron being present in the colorless form.
He also gives an experiment where you run an grid test and it shows the
same amount of iron but the color changes from amber to black.
It is very interesting stuff.
Hope it helps,
John Britt
www.johnbrittpottery.com
Gary Harvey on fri 10 feb 06
not red ----Brown. Iron Oxide will turn brown in oxidation under a clear
glaze at cone 5-6. How do I know? I have some horrible mugs I thought
would be red that's why. Gary Harvey, Palestine TX
----- Original Message -----
From: "Philip Poburka"
To:
Sent: Friday, February 10, 2006 3:00 PM
Subject: Re: Why did the Red Iron Oxide disappear?
> Hi Fran,
>
>
> If memory serve...
>
> If it was fired in reduction...it would be making 'grey' where, in
> oxidation, 'red'
> would be.
>
> Might have been too thin an application of RIO also...if mere 'ghosts'
> remained...
>
>
> Phil
> Las Vegas
>
> ----- Original Message -----
> From: "Fran Schwartz"
>
>> Dear Clayarters,
>> A studio-mate of mine here in sunny San Miguel de Allende, Mexico
>> recently painted a number of pieces in places with RIO and in other
>> places
>> with Velvet Underglazes.After dipping into a transparent glaze and firing
>> to cone 05, the RIO had mostly disappeared, but a ghost of gray
>> remained.The Velvets were fine.
>> Can you tell us what happened to the missing RIO? And how to keep it
> from
>> disappearing?
>> Everything else here is wonderful.
>> Thanks for your help. Fran Schwartz
>>
>>
> ____________________________________________________________________________
> __
>> 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.
>
> ______________________________________________________________________________
> 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.
>
Jim Brooks on fri 10 feb 06
John Britt...is there an LOI factor with red iron? Jim in Denton..
John Britt on fri 10 feb 06
Jim,
I am not expert but there has to be LOI on red iron as it loses an oxygen.
Some of the chemists will know better.
Do you think that has something to do with the invisible phase Currie
talks about?
John Britt
www.johnbrittpottery.com
Jim Brooks on sat 11 feb 06
If the iron content it not large to begin with then the LOI might cause a
reduction in color..
Fredrick Paget on sat 11 feb 06
I would be very interested in an explanation for this. I have had the
same trouble with disappearing iron oxide images from laser printers
transferred to clay when I try to put a clear glaze over them. I
tried every clear glaze I could put my hands on with no good result.
The glaze decolorizes the iron image.
That is one reason I came up with ways to make a more robust image
out of Mason stains.
Maybe a brown Mason stain can substitute for the RIO in this case?
--
From Fred Paget,
Marin County, CA, USA
fredrick@well.com
http://homepage.mac.com/fredrick/FileSharing1.html
Charter Member Potters Council
May Luk (Yamerica) on sat 11 feb 06
Hello all;
I have no suggestions to Fran's studio colleague or the disappearing iron.
I do know that alumina and silica ratio is important to the colours of
high iron glaze. I went to Mike Bailey's glaze workshop last year and he
explained it very well. You can see it on Page 93 of his 'Oriental
Glaze' book. He does this 49 quadraxial line blend which is essentially
a currie grid.
If you want notes on how to make Mike Bailey's line blend as per his
method, you can email me off list.
Best Wishes
May
London, UK
Ivor and Olive Lewis on sun 12 feb 06
Dear Jim Brooks,
You suggest <<....If the iron content it not large to begin with then =
the LOI might cause a
reduction in color...>>
Loss on Ignition usually is about Water of Crystallisation, Water of =
Hydration or the expulsion of an acid radicle such as CO2, SO3 or F. =
None of these are present in Iron oxide and as I recall the original =
post it would have been one of those in the original application.
This is an interesting idea. But I would like to know what is being lost =
and at what temperature does this happen. Also, are there any other =
factors involved ?
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Vince Pitelka on sun 12 feb 06
As Ivor explained, there is no LOI with red iron oxide. But as colorants
go, it is not one of the strongest, and is easily absorbed into the glaze if
not applied in sufficient concentration. That would explain how the color
was washed out in the glaze-fired piece. And if it is applied in high
concentration, the glaze often crawls away from the dry, powdery iron oxide.
For that reason, many potters choose to apply the RIO overglaze. The
disadvantage of the latter is that it is easily smeared when loading the
kiln, but with a little care that's usually not a problem.
Also, the effectiveness of red iron oxide brushwork has to do with the
amount of iron already in the glaze. With a traditional celadon, overglaze
iron brushwork will push the effect to a temmoku color. With a traditional
temmoku, overglaze iron will push it to a saturated iron like a kaki. Those
beautiful Chinese Sung Dynasty temmoku pieces with the irridescent iron
brushwork were the latter.
25 years ago I was doing a lot of decoration with iron and cobalt on
production ware (see
http://iweb.tntech.edu/wpitelka/gallery/railroad%20stoneware/railroad_stoneware.htm)
- doing banding in both iron and cobalt, and various brushwork designs with
cobalt. Initially I worked with RIO and cobalt carbonate washes (just oxide
and water) applied to the bisqueware. I had a lot of trouble with the glaze
crawling away from both of the oxides. In subsequent experimentation I
settled on doing the iron banding with a high-concentration iron slip (25%
RIO) on damp greenware, and the cobalt decoration with cobalt oxide on the
bisqueware under the glaze. That eliminated all the crawling, and I was
still able to achieve the bright iron red and dark almost-black cobalt blue.
This is a good example of how you must sometimes apply different stages of
decoration at different stages of drying and firing in order to achieve the
desired end result.
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
John Britt on sun 12 feb 06
Ivor,
I think iron does have some LOI, particularly yellow iron. I think it is
negligible but technically it does have some.
Also, since the materials we get are not pure, I think that even red iron
oxide will have some water associated with it so it will have a small LOI.
And, I also think that if you fire to cone 10, although this original post
was dealing with low fire, you loose oxygen, which is what makes oil spots
possible. So technically you should have some LOI there.
I know that this is negligible but I believe that this is true. What do
you think?
From the weekend chemistry arm chair,
John Britt
www.johnbrittpottery.com
dalecochoy on sun 12 feb 06
----- Original Message -----
From: "Vince Pitelka"
To:
Sent: Sunday, February 12, 2006 12:50 PM
Subject: Re: Why did the Red Iron Oxide disappear?
> 25 years ago I was doing a lot of decoration with iron and cobalt on
> production ware (see
> http://iweb.tntech.edu/wpitelka/gallery/railroad%20stoneware/railroad_stoneware.htm)
Vince,
I'd never gone to your site before. What wonderful work from you and your
students!
Regards,
Dale Cochoy
Wild ThingsBonsai Studio
Ivor and Olive Lewis on wed 15 feb 06
Dear Friends
John Britt wrote to me privately <LOI, particularly yellow iron. I think it is negligible but technically =
it does have some.>>=20
I sent John a private reply because I did not realise that his note to =
me could have been displayed on Clayart 2006-041 which I did not =
receive, Some of you may be interested in my response in which I wrote
<Ignition, in the form of Chemically Combined Water and also as Water of =
Hydration of
indeterminate proportions. But "Yellow Iron" is not an oxide, it is a =
Hydrated Hydroxide or an Hydrated Oxide with the molecular =
representation of Fe0(OH).nH2O or 2Fe2O3.3H2O depending on the =
reference chosen. It would be better if we called "Yellow Iron" by one =
of its mineral name, which are Limonite if you are "Ancient" or Goethite =
if you are "Modern", or if you wish to think "Amorphous" or =
"Crystalline".>>
Best regards,
Ivor Lewis.
Redhill,
South Australia.
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