Edouard Bastarache on sat 30 jan 10
> Directly from Smart.Conseil in France.
> The best ceramics technologist I know of.
> This was proved by my own works in New France.
> One year I tested many cone 9-10 redux clays,
> out of 250 that all contained Ferric Oxide,
> 33% were without any type of spar.
> And no problemo.
> I posted these results on Clayart a few years ago.
>
> Smart told me the explanation.
> If you fire in redux at cone 9, ferric oxide will
> be transformed into black iron oxide, a very powerfull
> flux that will attack the free silica and turn
> it into fayalite, preventing the formation of cristobalite.
>
> The other ceramicist who understood my results,
> was Gary Shafer, then living in the panhandle of Ohio,
> on the pottery chat, smart guy. He said something like :
> "You use Ferric Oxide as a fluxing material instead
> of spars, firing in redux."
> The key point is to fire in reduction.
>
> Gis,
>
> Edouard Bastarache
> Spertesperantisto (Lernu-Paris)
>
> Sorel-Tracy
> Quebec
>
> http://edouardbastarache.blogspot.com/
> http://www.flickr.com/photos/30058682@N00/
> http://cerampeintures.blogspot.com/
> http://albertpaintings.blogspot.com/
> http://perso.wanadoo.fr/smart2000/index.htm
>
>
>
>
>
> ----- Original Message -----
> From:
> To: "Edouard Bastarache"
> Cc:
> Sent: Saturday, January 30, 2010 2:41 PM
> Subject: Re: Dunting Problem
>
>
>> Hi Ed,
>>
>> Where did you get this information - my experiments show the opposite.
>> I have read also that iron oxide helps the production of cristobalite.
>>
>> It certainly lowers the melting point of clay bodies and therefore
>> limits the amount of spar you can use.
>>
>> RR
>>
>> Quoting Edouard Bastarache :
>>
>>
>>> in reduction, ferric oxide will do the same to convert
>>> free silica to fayalite and prevent the formation of cristobalite.
>>>
>>>
>>> Gis,
>>>
>>> Edouard Bastarache
>>
>>
>>
ivor & olive lewis on sun 31 jan 10
I would support Edouard on the reactions between Black Iron oxide (FeO) or
Black Iron oxide (Fe3O4) known as Magnetite and free Silica to generate
Fayalite (2FeO.SiO2)
The partial pressure of Oxygen has to be very low. According to the phase
diagram for the system FeO-Fe2O3-SiO2 I would estimate the partial pressure
would be below 10exp minus 9 atmospheres in the region of Cone 6. Fayalite
has a mp of 1205 deg C.
The lowest Eutectic reaction in that region of the diagram is given as 1140
deg C.
Best regards,
Ivor Lewis,
Redhill,
South Australia
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