Dov Katz on wed 21 mar 01
Hello Clayarters,
Has there been any discussion of using a gas such as CO2 etc. for reduction
of raku pieces (as opposed to traditional reduction with combustibles)? The
hot piece would be put in a chamber that would then be filled with the
reduction gas. This would appear to be a more controllable form of reduction
with no scarring effects etc. if it would work.
Any comments or article references appreciated.
TIA
Dov Katz
Victoria, BC
Canada
Tom Buck on thu 22 mar 01
Louis:
Sometimes the obvious is hard to see. Yes, 5% H2 + 95% N2 would
serve as a reducing agent without the danger of explosion (the lower limit
for H2's self-ignition in air is just above 5%).
But where would the typical raku potter find such a mixture? and
if they did, what would be the cost?
Today's newspaper is tommorow's fishwrapper, or the day after's
raku reducing agent.
bye. peace. Tom.
Tom Buck ) tel: 905-389-2339
(westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street,
Hamilton ON L8T 3E1 Canada
Bruce Girrell on thu 22 mar 01
> Has there been any discussion of using a gas such as CO2 etc. for
> reduction
> of raku pieces (as opposed to traditional reduction with
> combustibles)?
CO2 would not provide reduction, though it may prevent reoxidation of an
already reduced piece. For reduction you would need CO or some other
reactive substance that wants oxygen.
Reduction is not about the exclusion of oxygen; it is about some material
wanting oxygen more than the metal oxides that we glaze the pot with. That
oxygen-hungry material then "steals" the oxygen from the metal oxide,
thereby reducing the metallic oxide to a base metal.
Bruce "oxygen thief in the night" Girrell
Louis Katz on thu 22 mar 01
At an NCECA several years ago a man from somewhere in Great Britain, gave a talk
on reduction using a commercial mixture of gases containing 5% Hydrogen and 95
percent nitrogen. CO2 is not a reducing agent I think you are thinking of CO.
Louis
> Has there been any discussion of using a gas such as CO2 etc. for reduction
Edouard Bastarache on thu 22 mar 01
Hello all,
In one of the steel plants I work for we use daily 200,000 cubic feet of
a gas having the following composition :
35% carbon monoxide
55% hydrogen
10% a mixture of nitrogen and carbon dioxide.
This gas mixture is used to reduce iron ore pellets to metallic iron
before being put in150 ton electric furnaces in order to make steel.
We call the furnaces (2) where reduction takes place: =AB reduction plant=
s =BB .
You have to climb 345 stairs to get to the top.
It reminds of the process used to fire pots in reduction.
Later,
Edouard Bastarache
Irr=E9ductible Qu=E9becois
Sorel-Tracy
Dans / In "La Belle Province"
edouardb@sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/~edouardb/
iandol on sat 24 mar 01
Dear Dov Katz,
First of all, I am not sure that it is Carbon Dioxide which causes =
reduction. I have always read the this gas is the result of reduction.
It is usually said that Carbon Monoxide is responsible for the reduction =
of coloring metal oxides and carbonates in glazes. However, this is a =
highly combustible gas, capable of causing explosions if ignited with a =
supply of oxygen or air in an enclosed space. Furthermore it is =
poisonous and a major health hazard.
To make this work, you would need to put your hot pot in a chamber, seal =
it, flush out all air with an inert gas, then flush the chamber with =
carbon monoxide, hydrogen or a hydrocarbon gas such as methane, coal gas =
or evaporated alcohol. Having achieve reduction it would be necessary to =
reverse the gas flushing process to clear unused reducing gas before =
opening your chamber and admitting air.
One point which may not have been thought of before is the use of water =
as a potential reducing agent. Heated steam, passed over red hot iron =
powder oxidises the iron leaving hydrogen as a product. Again, there is =
the potential of an explosion so the usual precautions would be needed. =
But it would give a ready supply of reducing gas.
Perhaps the popular ways are best after all.
Best regards,
Ivor Lewis. Redhill, South Australia.
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