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iron chromate blue?

updated mon 6 oct 08

 

Ron Roy on sun 5 oct 08


I am posting this for someone else - does anyone have any idea what is
happening here?

Thanks - RR

>I recently tried mixing a glaze recipe that was given to me by a friend and
>have come up with what i think is a very
>unusual reaction. I am hoping you can help me determine why this is
>happening. The recipe for the glaze is as
>follows:
> F4 Feldspar 626.1
> 325 Mesh Silica 478.3
> Frit 3134 478.3
> Calcium Carbonate 106.3
> Gerstley Borate 95.7
> OM-4 69.1
> Nepheline Syenite 33.2
> Iron Chromate 56.5
> Copper Carbonate 56.5
>
>
>When mixing this glaze I realized at the end when adding the colorants that
>i did not have enough Copper
>Carbonate to finish the batch. I left it out intending on purchasing some
>more to add but decided to fire a test of it
>to see what the results were without the copper (as i like to experiment
>with glaze compositions) and wound up with
>a very nice blue glaze that breaks well on texture. I have been trying to
>determine why i got the blue result from it
>as there is nothing in the glaze that should result in the bright blue
>coloring i get. Can you offer any suggestions as
>to why this is occurring? The glaze also seems to be quite fluid at cone 6
>(actually probably a little closer to a cone 7
>is where i fire) when applied thickly. The glaze seems to be fairly
>stable when fired. Any input you could offer on
>this would be greatly appreciated as well as any points i should be
>concerned about as most of our pieces as
>functional and for everyday use.
>
>Thanks in advance,
>Bobby Childs

Ron Roy
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0