Edouard Bastarache Inc. on thu 30 nov 06
Bruce,
since you are an engineer you will understand this
"charabia" more than me:
"Determination of the Reduction Mechanism by
Temperature-Programmed Reduction-- Appication to
Small Fe2O3 Particles"
http://pubs.acs.org/cgi-bin/abstract.cgi/jpchax/1986/90/i07/f-pdf/f_j100398a025.pdf?sessid=6006l3
Later,
Edouard Bastarache
Le Français Volant
The Flying Frenchman
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.pshcanada.com/Toxicology.htm
http://www.flickr.com/photos/30058682@N00/
Bruce Girrell on fri 1 dec 06
Edouard,
Thank you for that link. Unfortunately, I don't see any more than the
abstract and the introduction (but it is interesting to note that they
comment on the effect of water in the reduction reaction).
I think this may actually be easier to deal with experimentally.
1) Sprinkle red iron oxide powder on some test tiles
2) Fire in a reduction environment to 1050 degrees
3) Starting at about 800 degrees, pull a tile each 50 degrees
4) Remove each tile to a closed container with dry ice to cool in an
oxygen-free environment
5) Examine visually for evidence of a change in color
Some thoughts:
1) I wonder if there would be any difference observed between iron powder on
an already bisqued tile vs. iron powder sandwiched between unfired slabs of
clay (more closely simulating the condition of iron particles in the body of
a clay object).
2) Would the brief introduction of oxygen due to opening the kiln door
adversely affect the experiment? Pulling through a spy hole may be possible,
but much more difficult.
3) Will visual examination of the results be adequate? How much reduced iron
does it take to cause black coring?
4) I don't see any means to run a control group in the same firing. I am
thinking that a control would consist of red iron fired in an oxidizing
environment.
5) What could be done to go further? Fire these tiles in a glaze firing and
check for black coring? If reduction of iron during bisque is the problem,
why does an oxidizing bisque cure the problem? The iron doesn't go away. Why
is it not reduced and cause black coring in the glaze firing? Does the black
coring come from two shots of reduction? Does it come from the presence of
carbon causing local reduction (my original supposition)?
6) What effect would the composition of the tiles have? Should they be
porcelain clay to isolate observations to the red iron powder and minimize
iron effects from the clay or should they be a higher iron content clay to
more closely approximate real world conditions?
I welcome any input from those who care about such things.
Bruce Girrell
Is it known approximately to what temps the Greeks fired their blackware?
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