NELSON@GEORGE.BAKERU.EDU on thu 14 nov 96
WPCF
ORP_PTR51_DRS.DR
Funny you should ask about Floating
Red because I was going to ask about this very glaze. I have tested it in cone
id want to ask about the glaze because it needs to be put on very thick to get t
nd it runs a great deal. When it is thin it is nothing spectacular. I decided
t the bottom of bowls it is quite nice. I hadn't noticed or thought about that
ecipe I used ) I rounded off the percentages.
FLOATING RED (from Clayart) cone 6 oxidation
Gerstley Borate 55
Talc
15
Flint 30
____
100
Red Iron Oxide
22
The question I wanted to ask was does the floating red come about because of t
is it a result of the red iron oxide? If you added some alumina to this glaze,
aze is made up of so much flux? It would stop the amount of running on vertical
r qualities if you stiffened it up.
I did get some pinholing when it was so thick on some of my bowls, but I think
be because I got it on too)o)o)o thick, trying for the effect.
Phyllis
Baldwin City, KS
e)mail: NELSON@george.bakeru.ed
bill edwards on thu 21 apr 05
I see potential for iron release. So cooking in iron
pots also has release. Some people are sensitive to
iron in overloads? Toxic, not a known issue with iron
unless a vast quantity is involved. Get E.B. in Canada
in on this.
GB would be the issue with some solubles.
Over-saturation or a metallic compound and would the
glaze be able to hold that much in? Extraction tests
by a lab would be the only true scientific way to
examine this completely. So yes, I believe some level
of leaching will happen, how much is too much? Each
firing or different kiln and each load of GB would
produce some variations and each test would give
various results. Can you reduce the GB out and get the
same results using a fritted material thats more
stable?
If Ron or some other person misses this post and
doesn't present a calculated response let me know
off-list and I will work it up in the best laymans
terms I can and send you the calculated results. You
would need to test this in other ways which I can
explain as well as upon firing. I don't see a toxic
problem, I do see some leaching and perhaps a better
way to formulate this with better results. I have zero
desire to start back calculating on line however, but
will try to help anyone I can, when I can, because I
would like to see more people move to the front and
place their recipes out there so they can be made
better and do more experimenting to produce high
quality glazes. I fired myself from my old job a few
years back and took an early retirement from glaze
guruing but am not dead yet! I'm still having near
life experiences on occasion. Lol
Bill Edwards
Edmar Studio and Gallery
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Edouard Bastarache Inc. on thu 21 apr 05
Iron oxide and hematite
Iron (Fe) is an abundant metal, constituting about 5% of the earth's crust.
Common iron ores are:
1-Hematite (Fe2O3),
2-Magnetite (Fe3O4),
3-Limonite (Fe2O3.H2O),
4-Siderite (FeCO3).
Of importance is that most ores mined may contain between 10% and 12% free
silica.
Iron compounds have many applications , and iron oxide pigments are used in
coatings
and as colorants in ceramics, glass, plastics, rubber and the like.
Environmental Levels and Exposure :
A-Soil :
In comparison to most other metals, the average concentration of iron in
soil is very high,
5000 mg/kg.
B-Air :
In remote and non-industrialized areas of the world, the atmospheric
concentration is less
than 1 ng/m³.Higher values are found in urban areas and close to iron- and
steel-producing plants.
C-Diet :
The daily intake of iron varies greatly with the proportions of iron-rich
and iron-poor
items that comprise the diet, but in most industrial countries, it typically
ranges from
9 to 35 mg/day.
Uptake and Distribution :
Iron is an essential metal and takes part in oxygen transport and
utilization. Absorption
of iron from the gastrointestinal tract is adjusted to a fine homeostasis.
Under normal conditions, about 5% to 15% of iron in food is absorbed, but
the uptake
increases considerably in the case of iron deficiency or depleted iron
stores.
Normally, the human body contains about 3 to 5 g of iron. Two thirds of this
amount
is bound to hemoglobin in the blood.
About 20% to 30% iron in the body is stored in storage proteins (ferritin
and hemosiderin)
Elimination is slow and takes place mainly via bleeding and by desquamation
of mucosal
cells
Increased gastrointestinal uptake and deposition of iron in various organs
may lead to secondary lesions in these
organs. In other diseases, iron deposition is a sequella of pathologic
processes.
A-Hemochromatosis :
A hereditary metabolism anomaly characterized by increased absorption of
iron
which ends up after the age of fifty in cutaneous pigmentation, liver
cirrhosis
and sometimes diabetes. Other organs may be affected:
-pituitary,
-gonads,
-heart,
-articulations.
B-Secondary hemosiderosis :
One usually distinguishes hemosiderosis, which is an iron overload of
tissues, from hemochromatosis which comprises tissue lesions due to martial
(iron) accumulation.
1-Generalized :
It may be secondary to chronic hemolysis, sideroblastic anemias, excessive
iron intake by parenteral route or, in the case of sideroblastic anemia, by
oral route.
It is also found in Kashin-Beck's disease, a disease encountered in regions
where drinking water is very rich in iron salts.
2-Localized :
· within the lungs, due to repetitive hemorrhages as in mitral
stenosis, in idiopathic pulmonary hemosiderosis;
· within the kidneys, as in intravascular hemolysis, paroxysmal
nocturnal hemoglobinuria;
· within the liver, in porphyria cutanea tarda.
Occupational exposures to iron occur during mining, both underground or
open-pit, in iron and
steel foundries, during arc-welding, in connection with various metal
processing activities;
and in silver polishing (using fine iron oxide as a polishing rouge).
Toxic Effects
A-Ingestion :
Ingestion of soluble iron salts, such as those found in common iron tablets
taken in the
treatment or prophylaxis of iron-deficiency anemia, are potentially very
toxic.
In doses exceeding 0.5 mg of iron, toxic effects with vomiting, ulceration
of the gastro-
intestinal mucosa, and intestinal bleeding may occur. In severe cases, liver
and kidney
damage may also develop.
B-Inhalation :
1-Siderosis:
Inhalation of iron, mainly in the form of iron oxide fumes, can give rise to
roentgenologic
changes in the lung due to deposition of inhaled iron particles. The
retained dust produces
x-ray shadows that may be indistinguishable from fibrotic pneumoconiosis. It
has been
named siderosis, iron pneumoconiosis, hematite pneumoconiosis, iron
pigmentation
of the lung, and "arc welder's lung", reflecting the fact that it has been
seen in many occupational groups exposed to iron oxide fumes, including
silver polishers.
Most specialists regard these roentgenologic lung changes to be benign
without having any
influence on the lung function or progressing to fibrosis.
2-Sidero-silicosis:
Siderosis is sometimes associated with silicosis among iron ore
miners if the exposure to free silica is severe enough to cause fibrotic
changes and subsequent
deterioration of the pulmonary function.
Carcinogenesis:
Altough an increased incidence of lung cancer has been observed among
hematite miners
exposed to iron oxide, presumably as a result of concomitant radon gas
exposure, there
is no evidence that iron oxide alone is carcinogenic to man or animals.
In a large (10,403) cohort study of Minnesota iron ore (hematite) miners,
they did not show
any increased mortality in lung cancer. This study is of particular
interest, for the radon levels
in Minnesota iron ores, in contrast to most of the other iron ore mines
examined, was low.
In addition, smoking was prohibited underground, and diesel fuel vehicles
were not used.
No evidence was found in a study for an increased lung cancer risk in a
plant producing
sulfuric acid from pyrite (FeS2) where workers had been exposed to iron
oxide dust at
very high concentrations (50 to 100 mg/m³.
Thus it seems reasonable to conclude that iron oxides are not carcinogenic.
Quebec's exposure limit:
VEMP (Valeur d'Exposition Moyenne Pondérée) = 5mg/m³
References :
1-Occupational Medicine,Carl Zenz, last edition.
2-Clinical Environmental Health and Toxic Exposures, Sullivan & Krieger;
last edition.
3-Sax's Dangerous Properties of Industrial Materials, Lewis C., last
edition.
4-Toxicologie Industrielle et Intoxications Professionnelles, Lauwerys R.R.
last edition.
5-Chemical Hazards of the Workplace, Proctor & Hughes, 4th edition.
"Ils sont fous ces quebecois"
"They are insane these quebekers"
"Están locos estos quebequeses"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
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