[Clayart] white glaze (^6, Ox)

[Edouard Bastarache]

There is nothing toxic in this base

Plejkore,

Edouard Bastarache
Spertesperantisto

My Books :
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http://quebecstonewareglazesii.blogspot.ca/










----- Original Message ----- 
From: <ronroy at ca.inter.net>
To: "Clayart international pottery discussion forum" 
<clayart at lists.clayartworld.com>; "Madeleine Hall-Arber" <arber at mit.edu>
Cc: <clayart at lists.clayartworld.com>
Sent: Saturday, April 07, 2018 1:23 PM
Subject: Re: [Clayart] white glaze (^6, Ox)


>
> Hi Madeleine,
>
> There was not much difference when you subbed in Min spar for the F4 - 
> certainly not enough to make it matte. Did those kiln loads cool  slower 
> than usual?
>
> This glaze is not stable by the way - short of both alumina and  silica. I 
> would not recommend it as a liner glaze.
>
> You should mix up a mall batch to see if you made a mistake.
>
> This one is a bit closer to the original.
>
> 19.50  DOLOMITE
> 13.00  GERSTLEY BORATE (Laguna June 2011)
> 26.00  SILICA
> 41.00  FELDSPAR MINSPAR 200 (soda)
> 13.00  ZINC Oxide
> Total = 112.5
>
>
> 0.33* CaO
> 0.22* MgO
> 0.04* K2O
> 0.10* Na2O
> 0.31* ZnO
> 0.00  Fe2O3
> 0.00  TiO2
> 0.10  B2O3
> 0.15  Al2O3
> 1.85  SiO2
> Si:Al:  12.12
> SiB:Al:  12.76
> Thermal Expansion: 484.50
> Formula Weight: 196.24
>
> RR
>
> Quoting Madeleine Hall-Arber <arber at mit.edu>:
>
>>
>> I have used a glossy white glaze that runs a bit when thick, but has  a 
>> beautiful effect when dripped a bit over (or under) other glazes. 
>> Suddenly, it came out with a matt finish.  The first time, I thought 
>> maybe I hadn't quite reached ^6, but the second firing was clearly  ^6. 
>> It is possible, of course, that I made a mistake in mixing, but  was 
>> wondering if anyone knows if the switch from Kona F4 to Minspar  could be 
>> responsible? (I think that is the only change in chemicals  since the 
>> last time I mixed this glaze with the possible exception  of a new bag of 
>> silica.)
>>
>> White, glossy, ^6
>> Dolomite 19.5
>> Gerstley Borate 13
>> Silica 28.6
>> Feldspar Kona F4 (sub minispar) 39
>> Zinc Oxide 13
>>
>> Thanks,
>> Madeleine
>> P.s. I think I found the "Purple Bright" I asked about a few days  ago 
>> listed as "Bright Purple" in Britt's book!
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>
>
>
> Ron Roy
> ronroy at ca.inter.net
> Web page ronroy.net
>
>
> 


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