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Help With Test Glazes


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#1 Joseph

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Posted 09 December 2013 - 02:21 PM

I have been trying to formulate some of my own glazes with free materials. Thus far I have made a glaze consisting of subsoil from around my house and ashes 50/50 by weight. This glaze was fired to cone 10 bending to about 2 o'clock in my wood kiln. It came out all rough and scabby. I was wondering if I should try adding a flux or more glass former? or maybe something else entirely. 

 

I have another glaze made from the wet saw tailings at my local stone counter top installer this was mixed with ash and a binder clay 40/40/20 and has a similar problem.

 

thanks for the advice.

 

JOseph



#2 Marcia Selsor

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Posted 09 December 2013 - 05:45 PM

I used a glaze 50 gold art and 50 cherry wood ash to ^10. Beautiful sugary gold. I think you need to find some better source of free clay. Check a local stream bed, mud flats or someplace  where there are deposits of real clay as potters know. Sounds like your soils might a true grit.

 

Marcia



#3 jrgpots

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Posted 10 December 2013 - 12:38 AM

I agree with Marcia. You may want to see if the subsoil melts. Make 10 inch long bar of the soil. Let it dry, then fire it to cone 10. If it melts you have starting point. If not, try a ball clay to make your ash glaze. You can also find the % shrinkage of your clay this way.

Jed

#4 Joseph

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Posted 13 December 2013 - 12:02 PM

So you do not think an addition of ground glass or perhaps egg shells( aka calcium carbonate) would help? My understanding is that the calcium acts as a flux and would lower the melting point of the other materials but I don't know much. I have read several glaze books but since they primarily deal in store bought products they don't seem like that much help.

 

thanks

Joseph



#5 neilestrick

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Posted 13 December 2013 - 12:16 PM

Egg shells would only really work if you can get them ground down into a powder, if you want them the flux the glaze uniformly.


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#6 Joseph

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Posted 13 December 2013 - 12:18 PM

I can do that. It seems from what I have read you do not want to exceed 2% by weight? Also do the shells need to be calcined before hand or can they do that in the glaze? I guess they will give off co2 in the reaction?

 

Joseph



#7 neilestrick

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Posted 13 December 2013 - 02:55 PM

Having never used egg shells, I don't know if they need to be calcined. Calcining them may turn them to powder, though. There can be a lot more calcium in a glaze than 2%.


Neil Estrick
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