Joseph Herbert on sat 24 jun 00
Alisa in Denmark wrote:
I was just going through a raw materials list and I realize I am once again
confused by materials and translations. I have three types of feldspars.
Potash K2O Al2O3 6SiO2 mol. 556
General feldspar, forshammer (K,Na)2O Al2O3 6SiO2 mol. 540
Soda Feldspar (or soda ash norflot) NaO.Al2O3 6SiO2 mol. 524
These feldspars I use in my glaze recipes.
But, then I have bags of something also labeled Soda Ash. That is what I
used for the Soda Ash wash. It is clearly a different material than soda ash
feldspar. It is rougher, almost raw salt consistency and hardens in
clumps. What is that? more or less pure salt (natron) NaO?
Alisa,
Don't we just love that mixture of industrial jargon, technical chemical
terms, and geologic name practice that confronts us when we look at the
ceramic supply catalog. And then add a different language. I have read
that the Danes made significant contributions to English political
development (and some assumed contributions to the gene pool at the same
time) so the return of information, if not payment in kind, can be given
none-the-less. (There probably should be an Email font convention for
tongue-in-cheek)
There are several old terms for materials that have that ASH suffix on the
end. Soda Ash (sodium carbonate - Na2CO3) is one. My Microsoft bookshelf
tells me that the name comes from the practice of burning seaweed to produce
the material. To make things easy for us, Potash refers to both Potassium
Carbonate (K2CO3) and to Potassium Hydroxide (KOH). The same source tells
me that the evaporation (in a pot) of leachate from wood ashes is the source
of the Potash word. The other potash (KOH) is also called caustic potash
(and it really is caustic) possible because it was obtained from regular
potash by driving off the CO2 with heat. To make things more interesting,
potassium carbonate is also called Pearl Ash. Another version of Sodium
Carbonate (with water in the crystals) is called Washing Soda. To this we
can add Natron which is also Sodium Carbonate with 10 combined water
molecules in the crystals.
Calcium Oxide, obtained by "burning" limestone (calcium carbonate) is just
called "Lime" or "Quicklime" which is kind of unfortunate because powdered
limestone is also called 'Lime." Of course for us, powdered calcium
carbonate is called "Whiting". Heating Whiting should give you "Whiting
Ash" but it doesn't it gives you Lime.
Two of your feldspars seem to have what may be geologic (or place) names
attached. The forshammer and norflot may be that kind of thing. In the US,
we have things like Kingman feldspar (a place in Arizona), Custer feldspar
(probably from Montana), Albany slip (actually we don't have it any more but
it did come from new york). These place (or person) names all refer to
things that have more or less specific compositions, but the names say
nothing about what those compositions might be.
Just to make things a little more complicated, there is an old chemical
convention of calling oxides of things by names that end in "ia" or "a." So
this gives us names like Silica, Alumina, Lithia (for Lithium Oxide), rarely
Calcia (for calcium oxide or lime), and maybe Titania (for Titanium dioxide
and also the faerie queen in Midsummer's might Dream). Some of the reason
these names are attached to materials is the former practice of reporting
the analysis of a compound in the equivalent oxides.
In any event, these names are, at best imprecise. If possible, one should
rely on a chemical formula for the material. This is not always possible so
it may be necessary to ask the supplier for more specific information. This
can be of specific interest during glaze formulation. The weights per unit
amount of desired oxide of these different materials varies greatly
depending on the presence of carbonate (44 mw extra weight over just oxide)
or extra water in the crystal (18 mw extra per water molecule). So the
names are very confusing and the correct chemical formula is the only way to
be really sure of what is there.
This is probably not all that helpful but it should clarify why you are
confused.
Joseph Herbert
Alisa and Claus Clausen on sun 25 jun 00
WOW!
Thanks, I appreciate that you went to the trouble to explain all this to =
me and you understand why it is confusing1
Dear Joseph,
Thanks for that great explanation.
I have broken my felsdspars down to three types on my shelf-
potash, sodafeldspar and one that combines both I call general...
As for the soda ash, it is just for wash.
Man, it is good we do not use our entire brains because I am only =
hopeful mine has reserve room to learn all this!
Thanks again,
Alisa
-----Oprindelig meddelelse-----
Fra: Joseph Herbert
Til: CLAYART@LSV.CERAMICS.ORG
Dato: 25. juni 2000 15:59
Emne: Soda Ash and other names
>Alisa in Denmark wrote:
>
>I was just going through a raw materials list and I realize I am once =
again
>confused by materials and translations. I have three types of =
feldspars.
>
>Potash K2O Al2O3 6SiO2 mol. 556
>
>General feldspar, forshammer (K,Na)2O Al2O3 6SiO2 mol. 540
>
>Soda Feldspar (or soda ash norflot) NaO.Al2O3 6SiO2 mol. 524
>
>These feldspars I use in my glaze recipes.
>
>But, then I have bags of something also labeled Soda Ash. That is what =
I
>used for the Soda Ash wash. It is clearly a different material than =
soda ash
>feldspar. It is rougher, almost raw salt consistency and hardens in
>clumps. What is that? more or less pure salt (natron) NaO?
>
>Alisa,
>
>Don't we just love that mixture of industrial jargon, technical =
chemical
>terms, and geologic name practice that confronts us when we look at the
>ceramic supply catalog. And then add a different language. I have =
read
>that the Danes made significant contributions to English political
>development (and some assumed contributions to the gene pool at the =
same
>time) so the return of information, if not payment in kind, can be =
given
>none-the-less. (There probably should be an Email font convention for
>tongue-in-cheek)
>
>There are several old terms for materials that have that ASH suffix on =
the
>end. Soda Ash (sodium carbonate - Na2CO3) is one. My Microsoft =
bookshelf
>tells me that the name comes from the practice of burning seaweed to =
produce
>the material. To make things easy for us, Potash refers to both =
Potassium
>Carbonate (K2CO3) and to Potassium Hydroxide (KOH). The same source =
tells
>me that the evaporation (in a pot) of leachate from wood ashes is the =
source
>of the Potash word. The other potash (KOH) is also called caustic =
potash
>(and it really is caustic) possible because it was obtained from =
regular
>potash by driving off the CO2 with heat. To make things more =
interesting,
>potassium carbonate is also called Pearl Ash. Another version of =
Sodium
>Carbonate (with water in the crystals) is called Washing Soda. To this =
we
>can add Natron which is also Sodium Carbonate with 10 combined water
>molecules in the crystals.
>
>Calcium Oxide, obtained by "burning" limestone (calcium carbonate) is =
just
>called "Lime" or "Quicklime" which is kind of unfortunate because =
powdered
>limestone is also called 'Lime." Of course for us, powdered calcium
>carbonate is called "Whiting". Heating Whiting should give you =
"Whiting
>Ash" but it doesn't it gives you Lime.
>
>Two of your feldspars seem to have what may be geologic (or place) =
names
>attached. The forshammer and norflot may be that kind of thing. In =
the US,
>we have things like Kingman feldspar (a place in Arizona), Custer =
feldspar
>(probably from Montana), Albany slip (actually we don't have it any =
more but
>it did come from new york). These place (or person) names all refer to
>things that have more or less specific compositions, but the names say
>nothing about what those compositions might be.
>
>Just to make things a little more complicated, there is an old chemical
>convention of calling oxides of things by names that end in "ia" or =
"a." So
>this gives us names like Silica, Alumina, Lithia (for Lithium Oxide), =
rarely
>Calcia (for calcium oxide or lime), and maybe Titania (for Titanium =
dioxide
>and also the faerie queen in Midsummer's might Dream). Some of the =
reason
>these names are attached to materials is the former practice of =
reporting
>the analysis of a compound in the equivalent oxides.
>
>In any event, these names are, at best imprecise. If possible, one =
should
>rely on a chemical formula for the material. This is not always =
possible so
>it may be necessary to ask the supplier for more specific information. =
This
>can be of specific interest during glaze formulation. The weights per =
unit
>amount of desired oxide of these different materials varies greatly
>depending on the presence of carbonate (44 mw extra weight over just =
oxide)
>or extra water in the crystal (18 mw extra per water molecule). So the
>names are very confusing and the correct chemical formula is the only =
way to
>be really sure of what is there.
>
>This is probably not all that helpful but it should clarify why you are
>confused.
>
>Joseph Herbert
>
>________________________________________________________________________=
______
>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 =
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