Paul Lewing on mon 13 may 02
I've been wondering lately about the differences in alkalinity of the
various flux oxides and their effect on color, particularly on iron oxide.
I have a few questions, based partly on Hamer & Hamer's text under
alkalinity. They list the strong alkalis as Li, Na, and K, and the weaker
alkalis as Mg, Ca, Sr, Ba, and Pb.
Question 1. I knew they fell into these two groups, but is this a ranking,
or just a random ordering of the two groups? And if it is a ranking, are
there empiric values for this, and how would those be determined? And are
there marked differences between the alkalinity of the oxides in each group?
Question 2. Does anybody know if there are differences in color response to
various colorants, not only iron but all of them, due solely to the
alkalinity of the flux oxides?
Question 3. This one's for GlazeChem users. I believe this program has a
number that supposedly indicates how alkaline a glaze is. Does anyone know
if this is true, and if so, is it a measurement or just a ranking? And have
you found it to be a useful predicter of anything?
I'm looking for clues to developing what has become the Holy Grail of glazes
for me, a stable, dependable, glossy bright iron red at cone 4 oxidation.
And, yes, I've tried every one of those Ca/Mg/B2oO3, low-Al2O3/high SiO2
matte reds. I want something different than that.
Thanks,
Paul Lewing, Seattle
Tom Buck on tue 14 may 02
Paul:
I can offer a view on your query of alkalinity. One part of
Chemistry is the study of Acids, Bases, and Salts, and their ocurrence in
aqueous (water) solutions.
What happens if you place in water, the following pure metals:
Lithium, Sodium, Potassium, Rubidium, Cesium? They all immediately react
with the water, the first most vigorously, almost explosively. They attack
the water molecule to form hydrogen gas, which escapes, leaving two types
of electrically charged components, labelled "ions": M+ and [OH]- and we
then say the solution is alkaline; hence the name alkali metals.
a similar action occurs with Magnesium, Calcium, Strontium, and
Barium as metals, but the reaction is less violent. again M++ ions and
[OH]- ions remain in the solution. but the M++ ions are less active than
the M+ ions. Historically, the name alkaline earth metals was used to
describe them.
Alakalinity, therefore, is a catchall word used to denote the
presence of M+ or M++ ions in aqueous solution, and the absence of any
acidic radicals (ions too).
To explain the underlying causes of this behaviour, one needs to
venture into some of the basics of quantum mechanics that set up a model
of atomic structure. This is too hairy for me. Let it suffice that the
electron shells (positions) around the central nucleus determine whether
an atom will form alkaline solutions. One descriptive idea used to handle
the differences between alkali and alkaline earths atoms is the term
"ionic radius" ...this provides a measure of alkaline activity. From this
term one can make a table listing the strength of alkali behaviour.
Lawrence has a table of ionic radii in his book, Science for the
Potter. So please refer to it.
I will stop now. and send this to you. more (perhaps) later.
Peace. Tom.
Tom Buck ) -- primary address. "alias"
or secondary address.
tel: 905-389-2339 (westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street, Hamilton ON L8T 3E1 Canada
Dave Finkelnburg on tue 14 may 02
Paul,
The order you list the elements in your question is a ranking, not a
random list. As Hank Murrow has mentioned, the answer is in the Periodic
Table of Elements. Li, Na and K are in increasing order of size and atomic
weight. Same for Mg, Ca, Sr and Ba. All of these are considered "metals"
as is the Pb, but I'm not sure how to explain the latter's effect, since
it's in a third group on the other side of the table.
Your other questions are excellent, by the way! Also way over my head!
As Hank says, try bone ash. Say 0.1 moles for starters.
Regards,
Dave Finkelnburg in drought-stricken Idaho where we're not
troubled by the snow you have (drool) in the Cascades
-----Original Message-----
From: Paul Lewing
>I've been wondering lately about the differences in alkalinity of the
>various flux oxides and their effect on color, particularly on iron oxide.
>I have a few questions, based partly on Hamer & Hamer's text under
>alkalinity. They list the strong alkalis as Li, Na, and K, and the weaker
>alkalis as Mg, Ca, Sr, Ba, and Pb.
>
>Question 1. I knew they fell into these two groups, but is this a ranking,
>or just a random ordering of the two groups? And if it is a ranking, are
>there empiric values for this, and how would those be determined? And are
>there marked differences between the alkalinity of the oxides in each
group?
Ruth Ballou on tue 14 may 02
Paul,
I don't know about effect of the alkalinity of the flux oxides on the
various colors at ^4, but I can tell you that alumina and silica have a
dramatic effect at ^6 and ^10. Ian Currie's grid method reveals marked
color changes caused by the varying alumina/silica ratio. The most dramatic
one is nickel. On the high alumina side of the grid it is pink, on the high
silica side it is blue, but other colorants are also impacted. Now maybe
this is really the alkaline/acid balance because the high alumina side is
also low in silica, allowing the alkaline fluxes to influence color. I
think you'll be surprised and amazed at the results if you deconstuct some
of your matte red glazes on the grid.
Ruth
Hank Murrow on tue 14 may 02
Paul Lewing wrote in part;
>I've been wondering lately about the differences in alkalinity of the
>various flux oxides and their effect on color, particularly on iron oxide.
>I have a few questions, based partly on Hamer & Hamer's text under
>alkalinity. They list the strong alkalis as Li, Na, and K, and the weaker
>alkalis as Mg, Ca, Sr, Ba, and Pb.
>
>Question 1. I knew they fell into these two groups, but is this a ranking,
>or just a random ordering of the two groups? And if it is a ranking, are
>there empiric values for this, and how would those be determined? And are
>there marked differences between the alkalinity of the oxides in each
group?
****Dear Paul; The Li,Na & K ions are known as the alkaline
fluxes, and the Mg, Ca, Sr,& Ba are known as the alkaline earth
fluxes. This is because the first three are in the fist column of the
Periodic Table of the Elements, relating to Oxygen 2-1. The alkaline
Earths relate to oxygen 1-1.
>
>
>Question 2. Does anybody know if there are differences in color response
to
>various colorants, not only iron but all of them, due solely to the
>alkalinity of the flux oxides?
****Yes, there are marked differences in color response.
David Stannard once made an elegant demonstration of this by
designing a glaze high in Alkaline fluxes and another high in the
Alkaline Earths. He glazed one side of a cylinder with the Alk glaze,
and the other side with the Alk Earth glaze and striped the cup with
a mixture of Cobalt and iron. the iron color dominated on the Li/Na
side, while the Cobalt dominated on the Mg/Ba side......same oxide
mix, but very different color response.
I have found that the fastest way to determine these
responses is by making and studying Currie Grid Tiles, with careful
control of the fluxes in the "C" corner. By the Way, do not overlook
the use of Phosphorus in getting your iron red color.
Best, Hank in Eugene
george koller on tue 14 may 02
paul,
we are working with soluble salts and looking for a red. per the arne
ase book (water colours on porcelain) cessium (he used as chloride)
will give a red. i am just set to test in next day or so. not cheap, but
some of these seem to go a long way. let me know if interested.
i wonder if FeCl2 will give a different color result than FeCl3 for a
some reason related to valency?
good luck in your quest!
best,
george koller
Paul Lewing wrote:
> I've been wondering lately about the differences in alkalinity of the
> various flux oxides and their effect on color, particularly on iron oxide.
> I have a few questions, based partly on Hamer & Hamer's text under
> alkalinity. They list the strong alkalis as Li, Na, and K, and the weaker
> alkalis as Mg, Ca, Sr, Ba, and Pb.
>
> Question 1. I knew they fell into these two groups, but is this a
ranking,
> or just a random ordering of the two groups? And if it is a ranking, are
> there empiric values for this, and how would those be determined? And are
> there marked differences between the alkalinity of the oxides in each
group?
>
> Question 2. Does anybody know if there are differences in color response
to
> various colorants, not only iron but all of them, due solely to the
> alkalinity of the flux oxides?
>
> Question 3. This one's for GlazeChem users. I believe this program has a
> number that supposedly indicates how alkaline a glaze is. Does anyone
know
> if this is true, and if so, is it a measurement or just a ranking? And
have
> you found it to be a useful predicter of anything?
>
> I'm looking for clues to developing what has become the Holy Grail of
glazes
> for me, a stable, dependable, glossy bright iron red at cone 4 oxidation.
> And, yes, I've tried every one of those Ca/Mg/B2oO3, low-Al2O3/high SiO2
> matte reds. I want something different than that.
>
> Thanks,
> Paul Lewing, Seattle
>
>
____________________________________________________________________________
__
> 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.
Hank Murrow on wed 15 may 02
>Tom Buck wrote in part;
>
> Let it suffice that the electron shells (positions) around the
>central nucleus determine whether
>an atom will form alkaline solutions. One descriptive idea used to handle
>the differences between alkali and alkaline earths atoms is the term
>"ionic radius" ...this provides a measure of alkaline activity. From this
>term one can make a table listing the strength of alkali behaviour.
> Lawrence has a table of ionic radii in his book, Science for the
>Potter.
Dear Tom and Paul;
As I posted privately to Paul, A further measure of an ion's
ability to disturb (flux) a network(glass)-former, is its Ionic
Potential. Ionic Potential is simply the ionic charge divided by the
ionic radius. Elements having an Ionic Potential larger than 7 are
considered network(glass)-formers, while those with Ionic Potential
less than 7 are considered network modifiers, that is, they disturb
the close -packing of the silica network (and the Phosphorus,
Titania, and Boron networks). The lower the Ionic Potential, the
stronger their ability to disturb (or flux) the network (glass).
Thus, K (0.75), then Na, then Li, then Ba. then Sr, then Ca, then Zn,
then reduced Fe, then Mg(2.6). Cardew has a nice discussion of this
on page 302 of "Pioneer Pottery", while Linus Pauling originated the
concept.
Again, I am making the case that The size of an ion coupled
with its charge (Ionic Potential) is a useful way to visualise its
r=F4le in altering a glass.
Cheers, Hank
iandol on wed 15 may 02
Dear Paul,
Who would know how Frank Hamer arrived at his list or what conclusions =
we can draw from them?
I note he says that his list is not necessarily linked to Ceramic =
Fusions but is more to do with their degree of activity in water.
Perhaps more would be revealed it you consulted his references, for =
example, Uvarov and Isaacs give "Alkali" as a soluble hydroxide of a =
metal or a substance that has an alkaline reaction to litmus in changing =
its colour to blue and that it can neutralise an acid in solution.
Lead oxide is, I understand, an Amphoteric oxide, giving rise to =
Plumbates with strong alkalies.
I think the answers to your questions are to be found in the glass =
technology books, or as others have suggested, obtained through an =
empirical approach.=20
All the best,
Ivor Lewis. Redhill, South Australia.
Paul Lewing on thu 16 may 02
on 5/15/02 7:44 AM, Hank Murrow at hmurrow@EFN.ORG wrote:
> The lower the Ionic Potential, the
> stronger their ability to disturb (or flux) the network (glass).
> Thus, K (0.75), then Na, then Li, then Ba. then Sr, then Ca, then Zn,
> then reduced Fe, then Mg(2.6).
So where does lead fit into this equation? Seems like it would be pretty
much at the opposite end off the spectrum from lithium, but it's about as
active a flux as it's possible to get.
Thanks, Paul
Wanda Holmes on thu 16 may 02
Paul, I am a GlazeChem user and I do plot the alkalinity ratios it produces
when comparing glazes. Unfortunately, I do not have enough test data yet to
draw any useful conclusions as how to use the ratio in a predictive fashion.
Like you, I'd like to hear from anyone who examined these numbers more
thoroughly.
The following is an example of the analysis GlazeChem gives for Tony
Hansen's 5x20.
Na2O 0.15 Al2O3 0.37 SiO2 3.51
K2O 0.07 B2O3 0.22 P2O5 0.00
MgO 0.03 TiO2 0.00
CaO 0.75 Fe2O3 0.01
Alumina:Silica ratio is 1.00:9.40
Neutral:Acid ratio is 1.00:5.90
Alk:Neut:Acid ratio is 1.00:0.60:3.52
Expansion: 69.4 x 10e-7 per degree C
Oxides causing abnormal expansion:
B2O3
Wanda
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
Behalf Of Paul Lewing
Sent: Monday, May 13, 2002 11:10 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Alkalinity of Glazes
I've been wondering lately about the differences in alkalinity of the
various flux oxides and their effect on color, ......
Question 3. This one's for GlazeChem users. I believe this program has a
number that supposedly indicates how alkaline a glaze is. Does anyone know
if this is true, and if so, is it a measurement or just a ranking? And have
you found it to be a useful predicter of anything?
Paul Lewing, Seattle
____________________________________________________________________________
__
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.
Hank Murrow on fri 17 may 02
>on 5/15/02 7:44 AM, Hank Murrow at hmurrow@EFN.ORG wrote:
>
>> The lower the Ionic Potential, the
>> stronger their ability to disturb (or flux) the network (glass).
>> Thus, K (0.75), then Na, then Li, then Ba. then Sr, then Ca, then Zn,
>> then reduced Fe, then Mg(2.6).
>
>So where does lead fit into this equation? Seems like it would be pretty
>much at the opposite end off the spectrum from lithium, but it's about as
>active a flux as it's possible to get.
>Thanks, Paul
Dear Paul;
Lead has an Ionic Potential of 1.5, placing it midway between
K @ .75, and Mg @ 2.6. As I have not used lead for 40 years,I just
pushed it out of my mind, in effect. I do not have an opinion about
its place in the scheme of things. Some years ago, David Stannard
(who I cited earlier) made a brass hexagonal bar with the relative
sizes of ions and their place along the bar located by their Ionic
Potential. Every once in a while, I study that bar and often a glaze
anomaly comes clear to me as I try to bring 'the bar' into alignment
with what I see coming out of the kiln. I truly feel that I.P. is the
great undiscussed, but immensely useful tool that would be good to
get our minds around.
Below is a message I received from David about the IP bar and
his referenced readings. Perhaps an answer is contained in them.
">Get Bob to dig out that Ionic Potential *sculptural bar* I
gave him, and
>close-up photo it with some good lighting. I think the unit
>distances(inches) measures from the brass O ion will
correspond to your
>I.P. differences(P, N, S, show up on the end, for reminder)
The Si+4, Al+3,
>Na+, etc., though, are at spread-out, weakening distances.
The I.P. is *an
>average intensity of attraction/ unit surface area of the
ion*-- the charge
>spread out over a larger ion is weaker/unit area, a larger charge
>concentrated over a smaller ionic surface builds a much stronger
>*intensity* of attraction(/unit area) for the O=, or other
anions. Maybe
>you can send a photo as attachment. Linus Pauling figured
out these simple
>arithmetic ratios, & I bet his book "The Nature of the
Chemical Bond" is
>still the most direct & simple treatment of Ionic Potential around.
>
>I got a *tremendous* lot of imagery out of the opening
chapters of Brian
>Mason's book "Principles of Geochemistry", 1st ed.(Wiley & Sons,
N.Y.,
>1952) I didn't like his revised edition-- better for geol.
students, maybe,
>but not for me.
>
>W.A.Weyl wrote a book, collected 1930s series of articles
from Ceram. Soc.,
>called "Colored Glasses" (Dawsons of Pall Mall, 1959) which
I found *very*
>useful for the static "network former/modifier theory"
treatment. Good for
>imagining competing color tendencies. Later he switched to Dynamic
>modelling-- more satisfying for professionals, & for me in
principle, but
>too hard to follow & make simple-minded shop use of it!)"
| |
|
