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tomhumf

10% black iron on dinnerware

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I'm working on a new raw glaze recipe. 

https://glazy.org/recipes/60373

Seems to be good so far, it's within the green and cooper limit formula for cone 7, and doesn't seem to scratch at all. 

The attached photos are with additions of 10% zirc silicate, and 10% black iron oxide ( not mixed very well) .

The black one has patches of very matt surface. I'm wondering if this would be a problem for dinnerware surfaces?

1581613738981.jpg

1581613738457.jpg

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Rub it with a fork, my main issue with mattes on dinnerware is that they usually mark with cutlery.

May want to taste it too, to make sure the saturated iron areas aren't metallic tasting (eww).

Other than that, nothing about iron as a colorant will poison people unless they have a rare genetic disease.  You can always send it out to be tested for amounts it may leech, iron does affect glaze melt and 10% is enough to do that.

Zirconium also has an effect on glaze melt, it's refractory.  It also is notorious for causing cutlery marking.

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5 hours ago, tomhumf said:

I'm working on a new raw glaze recipe. 

https://glazy.org/recipes/60373

Seems to be good so far, it's within the green and cooper limit formula for cone 7, and doesn't seem to scratch at all. 

The attached photos are with additions of 10% zirc silicate, and 10% black iron oxide ( not mixed very well) .

The black one has patches of very matt surface. I'm wondering if this would be a problem for dinnerware surfaces?

1581613738981.jpg

 

Looks nice and has a decent flux ratio so likely durable. I would like to see it fired lower and higher to learn more about the melt. Of course I would also like to see it tested in the microwave as well just to know if it posed any issues from that perspective.  From there a tiny bit  more boron might make this glossier if desired. Especially with the zircopax and heavy iron.

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Thanks all. I can't get any visible cutlery marks on the black one. The white does cutlery mark but not very easily and rubs off unless I attack it superhard with a knife. 

I've started using Zirc as an opacifier as I want a bright white in reduction. Previous tests show 7% is still quite white so I'll drop it down to that. 

Failing that I suppose I could flux more to reduce cutlery marking? It's not really a big problem but I'd prefer it not to happen. 

I'll make up some plates and do some more testing like your suggestions. 

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3 hours ago, tomhumf said:

Thanks all. I can't get any visible cutlery marks on the black one. The white does cutlery mark but not very easily and rubs off unless I attack it superhard with a knife. 

I've started using Zirc as an opacifier as I want a bright white in reduction. Previous tests show 7% is still quite white so I'll drop it down to that. 

Failing that I suppose I could flux more to reduce cutlery marking? It's not really a big problem but I'd prefer it not to happen. 

I'll make up some plates and do some more testing like your suggestions. 

Zircopax doesn’t melt so it often cutlery marks because the little itty bitty sharp edges stick up ( microscopically) and wear away your cutlery leaving a mark. Reducing the concentration may help and a smoother melt may help somewhat.  If these are going in reduction then I assume you will be firing to cone ten? Have they been  fired to that temp yet?

Edited by Bill Kielb

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Frances Senska always fired at ^7. She used a lot of local ingredients in her glazes. ^7 is a good temperature for a stoneware as long as it vitrifies. I converted to ^6 reduction when I was teaching at MSUB.  I fired to a flat ^6 from 1980 to 2000 at MSUB and lated at UT Brownsville. 

FYI Frances Senska taught at MSU Bozeman and was the teacher of Peter  Voulkos and Rudy Autio who became the first resident artists at Archie bray in 1951.

Calcium Carbonate or Whiting will harden a glaze surface from scratching.

Marcia

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