Snail Scott on mon 5 jan 04
At 10:42 PM 1/5/04 +0000, you wrote:
>...Snail,you are saying that things are different where you are. I guess
Zinc can do things differently with various potters...
Wasn't me. ;) -Snail
Earl Krueger on mon 5 jan 04
On Monday, Jan 5, 2004, at 09:39 US/Pacific, Stephani Stephenson wrote:
> It is amazing to see that in some cases the iron vanishes completely
> I do think the term 'bleaching' seems to describe process well , as in
> the calcium 'bleaches' out the iron this is something I can visualize,
> but what does this term, 'bleaching' really mean in terms of what is
> happening in the glaze?
Stephani,
I don't know if you saw my post from last night but in it I postulated
that the iron, at low concentrations, may be dissolving into a
colorless solution. Or, it is possible that the iron is forming a
colorless complex with other constituents of the glaze (Calcium?).
In the chemistry world there are many systems that behave as I will try
to depict in a graph;
( If this graph doesn't look very good try highlighting it and changing
the font to "Courier". )
C ^ |
O | | ------------
L | | /
O | | /
R | | /
|--------
-------------------------
Concentration
------------>
What happens is that as the concentration of a component increases
there is very little change in color, until a specific point is
reached. Then the color changes rapidly with just a small change in
concentration, until the color becomes saturated, at which point there
is very little further change in color as the concentration is
increased. This phenomenon is quite often used in chemical analysis in
the process called titration. The rapid change in color is used to
determine when a certain concentration of a substance has been achieved.
This phenomenon describes well what I have seen using iron oxide as
paint underneath some glazes. Low concentrations of iron bleach out
and then as the concentration increases the color switches rapidly to a
dark brown.
I've been tossing this idea around in my head today and I think I might
have a way to test this hypothesis. However, as it is #3 on my list of
tests to accomplish and I will need to build a piece of electronic
equipment, I probably won't get to it right away.
If I find out anything, I'll let you know.
Earl...
Bothell, WA, USA
Stephani Stephenson on mon 5 jan 04
I agree, the term 'bad' is somewhat misleading, as 'bad' would depend
on what your goal is in the first place.
I am not one to state broad 'rules' for glazes , as there are so many
variables, and I feel I will always be a
'student' where glazes are concerned..and also , as always, so MUCH
depends on your clay and clay body/glaze interaction
When I have tried to develop iron red/browns with non lead frits on a
red iron bearing clay, I have found
frits like 3134 tend to bring out greens from iron
1.e. cream colors have a greenish tinge to them
I, like Ababi, have found that a little zinc in the formula may
brighten up a brown glaze made with iron bearing brown stains
though the the zinc is perhaps also having this effect by acting on
chrome in the brown stains. but this is one material to experiment with
Also tin, as Ron mentioned, though tin in the kiln is sometimes
problematic if there is any neighboring chrome
Spodumene seems to promote reddish brown v. greenish browns from iron
in glazes too.
Does anyone know why?
one way to compare is to order small amounts of different frits , make
up some simple frit glazes with them
do some stripe tests with iron and iron stains over the frit glazes.
It is amazing to see that in some cases the iron
vanishes completely
I do think the term 'bleaching' seems to describe process well , as in
the calcium 'bleaches' out the iron
this is something I can visualize, but what does this term,
'bleaching' really mean in terms of what is happening
in the glaze?
Any takers on this question?
Stephani Stephenson
steph@alchemiestudio.com
piedpotterhamelin@COMCAST.NET on mon 5 jan 04
I like the versatility of iron.
Of course, it does depend on whether you are using the red "ferric" or black "ferrous" oxide.
Now ol'red does turn "yella" when it is in the presence of the bone shakin' calcia.
But when ol'red comes up to soda, when he just gets blue. Boric Oxide (boron the moron, is what he calls him) has the same effect on him.
No, Red likes it best when he get the lead in and kicks it up a notch with a potash and soda combo. Feeling good, the blood goes to his head and turns him red. No bashfulness here. Pure high blood pressure.
It has been said when Zinc mixes in, the whole thing becomes muddied but Snail,you are saying that things are different where you are. I guess Zinc can do things differently with various potters. I have seen muddied low fire transparent glazes with Zinc.
Of course, this is in the presence of a full blast of Oxy, no foggy reduction here!
Now the Black knight, Ferrous (Beuller?) melts more completely into the crowd and gets things going more fluid than ol'REd. Lithium gets him blue, unlike what it does for the general masses. Soda does the same. I get gas. Makes those folks in the room with me quite blue too.
Ferrous turns green when calcia, baria and potash are in the group. Sensitive guy.
Snail,in the cosmic realm of things, is it the fact that the Lithium has such a low atomic weight (and fluants it!) that it surrounds our Iron Maidens and makes them blush red? With an equal weight of Lithia you get over twice the amount of molecules than with Calcia..but no turning yellow. Do we have more oxidation (or something) happening in the molecular level since there are more lithia molecules at the party surrounding each iron molecule? Ganging up, in other words.
And then Calcia, if an equal weight, but half the molecules, makes the FE2 Red into 2FE2 yellow?
Going forward to where I know little but would like to know................
Rick
Mason stain used to publish a recommended base glaze listing with their colorants. Zinc was a notorious bad ass who would screw up alot of their colors.
--
"Many a wiser men than I hath
gone to pot." 1649
> I agree, the term 'bad' is somewhat misleading, as 'bad' would depend
> on what your goal is in the first place.
> I am not one to state broad 'rules' for glazes , as there are so many
> variables, and I feel I will always be a
> 'student' where glazes are concerned..and also , as always, so MUCH
> depends on your clay and clay body/glaze interaction
>
> When I have tried to develop iron red/browns with non lead frits on a
> red iron bearing clay, I have found
> frits like 3134 tend to bring out greens from iron
> 1.e. cream colors have a greenish tinge to them
> I, like Ababi, have found that a little zinc in the formula may
> brighten up a brown glaze made with iron bearing brown stains
> though the the zinc is perhaps also having this effect by acting on
> chrome in the brown stains. but this is one material to experiment with
>
> Also tin, as Ron mentioned, though tin in the kiln is sometimes
> problematic if there is any neighboring chrome
> Spodumene seems to promote reddish brown v. greenish browns from iron
> in glazes too.
> Does anyone know why?
>
> one way to compare is to order small amounts of different frits , make
> up some simple frit glazes with them
> do some stripe tests with iron and iron stains over the frit glazes.
> It is amazing to see that in some cases the iron
> vanishes completely
> I do think the term 'bleaching' seems to describe process well , as in
> the calcium 'bleaches' out the iron
> this is something I can visualize, but what does this term,
> 'bleaching' really mean in terms of what is happening
> in the glaze?
> Any takers on this question?
>
>
> Stephani Stephenson
> steph@alchemiestudio.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.
piedpotterhamelin@COMCAST.NET on tue 6 jan 04
Hi all
I mistakenly referred to Snail in my previous email when in fact I should have stated Stephanie. My apologies.
Rick
--
"Many a wiser men than I hath
gone to pot." 1649
> I like the versatility of iron.
> Of course, it does depend on whether you are using the red "ferric" or black
> "ferrous" oxide.
> Now ol'red does turn "yella" when it is in the presence of the bone shakin'
> calcia.
> But when ol'red comes up to soda, when he just gets blue. Boric Oxide (boron the
> moron, is what he calls him) has the same effect on him.
> No, Red likes it best when he get the lead in and kicks it up a notch with a
> potash and soda combo. Feeling good, the blood goes to his head and turns him
> red. No bashfulness here. Pure high blood pressure.
> It has been said when Zinc mixes in, the whole thing becomes muddied but
> Snail,you are saying that things are different where you are. I guess Zinc can
> do things differently with various potters. I have seen muddied low fire
> transparent glazes with Zinc.
> Of course, this is in the presence of a full blast of Oxy, no foggy reduction
> here!
> Now the Black knight, Ferrous (Beuller?) melts more completely into the crowd
> and gets things going more fluid than ol'REd. Lithium gets him blue, unlike what
> it does for the general masses. Soda does the same. I get gas. Makes those folks
> in the room with me quite blue too.
> Ferrous turns green when calcia, baria and potash are in the group. Sensitive
> guy.
> Snail,in the cosmic realm of things, is it the fact that the Lithium has such a
> low atomic weight (and fluants it!) that it surrounds our Iron Maidens and makes
> them blush red? With an equal weight of Lithia you get over twice the amount of
> molecules than with Calcia..but no turning yellow. Do we have more oxidation (or
> something) happening in the molecular level since there are more lithia
> molecules at the party surrounding each iron molecule? Ganging up, in other
> words.
> And then Calcia, if an equal weight, but half the molecules, makes the FE2 Red
> into 2FE2 yellow?
> Going forward to where I know little but would like to know................
> Rick
>
>
> Mason stain used to publish a recommended base glaze listing with their
> colorants. Zinc was a notorious bad ass who would screw up alot of their colors.
>
>
>
>
> --
> "Many a wiser men than I hath
> gone to pot." 1649
> > I agree, the term 'bad' is somewhat misleading, as 'bad' would depend
> > on what your goal is in the first place.
> > I am not one to state broad 'rules' for glazes , as there are so many
> > variables, and I feel I will always be a
> > 'student' where glazes are concerned..and also , as always, so MUCH
> > depends on your clay and clay body/glaze interaction
> >
> > When I have tried to develop iron red/browns with non lead frits on a
> > red iron bearing clay, I have found
> > frits like 3134 tend to bring out greens from iron
> > 1.e. cream colors have a greenish tinge to them
> > I, like Ababi, have found that a little zinc in the formula may
> > brighten up a brown glaze made with iron bearing brown stains
> > though the the zinc is perhaps also having this effect by acting on
> > chrome in the brown stains. but this is one material to experiment with
> >
> > Also tin, as Ron mentioned, though tin in the kiln is sometimes
> > problematic if there is any neighboring chrome
> > Spodumene seems to promote reddish brown v. greenish browns from iron
>
> > in glazes too.
> > Does anyone know why?
> >
> > one way to compare is to order small amounts of different frits , make
> > up some simple frit glazes with them
> > do some stripe tests with iron and iron stains over the frit glazes.
> > It is amazing to see that in some cases the iron
> > vanishes completely
> > I do think the term 'bleaching' seems to describe process well , as in
> > the calcium 'bleaches' out the iron
> > this is something I can visualize, but what does this term,
> > 'bleaching' really mean in terms of what is happening
> > in the glaze?
> > Any takers on this question?
> >
> >
> > Stephani Stephenson
> > steph@alchemiestudio.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.
>
> ______________________________________________________________________________
> 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.
iandol on wed 7 jan 04
Dear Stephani Stephenson,
You describe many of your experiences relating to the variations in =
colour or the absence of it in certain glazes or in association with =
differing elements and conclude..<>.. good =
question!!!
If we accept that a glaze is a glass which has been modified to suit our =
purposes and that it has undergone all of the processes which lead up to =
the final material; preparation, mixing and heating to get complete =
melting and cooling without forming any crystals or matness then the =
best starting point where one may learn about colour in Silicate systems =
is Woldemar A. Weyl, "Coloured Glasses", 1951.
First, quick generalised answer to your question is ...<< The affinities =
of atoms and ions for each other in combining into regular groupings can =
create entities which affect the behaviour of light which impinges on =
them. These entities are called "Chromophores" and they give distinctive =
colours to things>>...however...<produced by compounds of the transition elements, those we use for =
creating colour, owe this optical property to a deficiency of electrons =
in their penultimate outer electron shells...bit complex to understand =
!!!. Now if such atoms can acquire a sufficient number of electrons to =
fill the penultimate outer and eliminate the deficiency the ability to =
make colour will be robbed from them. My picture tells me that each Iron =
atom need another four electrons to make this work>>... Now that is the =
'Intuitive narrative
So, do we do this with Iron?. And if we do, what are we doing? To find =
out we need as complete a picture as possible. I don't have that so your =
guess is good as mine or anyone else's
Best regards,
Ivor Lewis. Redhill, South Australia
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