dreamsinclay on mon 19 apr 04
Needing some input on an RIO issue.
Had made a really nice glaze using a high % of RIO I
had for a long time....test pieces all came out great.
Today I mixed up another batch using a new bag of
Spanish Red only to find that the color of the two
batches of RIO were different.
The old stuff was real red.....and the new more brown.
When the glazes were mixed...the first came out a
rich red whereas the second more muted brown
My question is will the color of the RIO influence the
color of the glaze?
I wanted to fire up this kiln tomorrow...but am having
second thoughts until I hear from the forum.
I appreciate your thoughts...
Have a beautiful evening...
Denise
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Ron Roy on tue 20 apr 04
Hi Denise,
I do know that the colour of iron used can affect the final colour of the
glaze. Black iron will be different than red for instance in some glazes.
The purity of the iron may be the reason - keep in mind - slow cooling
brings out the reddish tone - you can test to see if a slower cooling will
improve the colour - just refire the glaze in a bisque firing - it will
give some indication if that is what is needed.
Impurities in some irons will help the crystals grow faster - maybe add a
pinch of rutile to help?
Does anyone know - the Spanish iron - more pure than the usual NA variety?
RR
>Needing some input on an RIO issue.
>Had made a really nice glaze using a high % of RIO I
>had for a long time....test pieces all came out great.
>Today I mixed up another batch using a new bag of
>Spanish Red only to find that the color of the two
>batches of RIO were different.
>The old stuff was real red.....and the new more brown.
> When the glazes were mixed...the first came out a
>rich red whereas the second more muted brown
>My question is will the color of the RIO influence the
>color of the glaze?
>I wanted to fire up this kiln tomorrow...but am having
>second thoughts until I hear from the forum.
>I appreciate your thoughts...
>Have a beautiful evening...
>Denise
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Lee Love on wed 21 apr 04
Ron Roy wrote:
>
>Does anyone know - the Spanish iron - more pure than the usual NA variety?
>
>
I recall John Reeve explaining that his synthetic Kaki included
Spanish iron because it was very fine. I also recall that it is
purer, being made from some kind of bacterial process with iron
sulfate. I searched the web and can find anything on the processing
of Spanish iron. A quick glance at Hamers and Chappel didn't turn
anything up (will look more closely after our morning walk,)
--
Lee in Mashiko, Japan http://mashiko.org
Ivor and Olive Lewis on thu 22 apr 04
Dear Friends,
I read the Chemistry of Iron Oxides is rather complex. Although we
think of Iron oxides in "Potter's Terms" as having simple whole number
proportions of 1:1 for FeO, 2:3 for Fe2O3 and 3:4 for Fe3O4 there is
some variation. You can get Fe0.84 to Fe0.95 for Black Iron Oxide
which is said to be unstable below 575=BA C when it will change to free
Iron and Fe3O4. Fe3O4 is sometimes regarded as a mixture of FeO and
F2O3. Fe2O3 is familiar to us as Haematite, which in its massive form
has a metallic lustre and a grey colour but when powdered has the tint
of Rouge, a strong dull dark red. If iron oxides come from reclaimed
scrap through being dissolved in acids and precipitation then you can
get Yellow Hydrated Iron oxides.
Add in the potential for contamination, alternative crystalline
phases and you are dealing with seemingly infinite variability. And
that is before considering the potential chemical reactions that can
occur during ceramic processing which can change the colour of a
glaze.
Best regards,
Ivor Lewis. Redhill, South Australia
----- Original Message -----
From:
To:
Sent: Thursday, 22 April 2004 2:22
Subject: Re: Spanish red!
> Hey everyone,
> Several years ago, I contacted a manufacturer who explained to me
what synthetic iron is.
> Your old 240GL volvo, the ford pinto, the dodge dart.
> Scrap iron is acidically fumed to corrode into the iron form that
you want to purchase. The purity can vary greatly; traces of arsenic
are allowable but controlled to ascertain whether it is becomes
ceramic, ink or paint pigment grade, cosmetic grade and even food
grade, I am certain, differing from animal food, human food or
vitamins.
> It is interesting to reflect that the iron grade that we dip our
hands into could contain more arsenic than the food grade. Perhaps we
should consider investing more money in purchasing the food grade for
glazes and have a little more assurance of safety. This manufacturer
recommended to me to purchase the dog food grade of iron as I am in
physical contact with the material.
> I assume a finer material as it assumes food grade.
> Of course, my pottery supplier knew nothing of this.
> Woof!
> Rick
>
> --
> "Many a wiser men than I hath
> gone to pot." 1649
>
>
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