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White Spots On Bisque-Fired Brown Clay


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#21 Tenyoh

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Posted 05 June 2014 - 11:25 PM

Jayne, thank you for sharing your technique. I currently have a leather-hard piece. I will experiment with the wet-sea-sponge technique on that.

 

I called my clay manufacturer today. They said clay with lots of iron oxide often causes scumming and recommended brown clay with less iron. I will let you know if the recommended clay will cause less scamming.



#22 Babs

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Posted 06 June 2014 - 01:59 AM

Jayne, thank you for sharing your technique. I currently have a leather-hard piece. I will experiment with the wet-sea-sponge technique on that.

 

I called my clay manufacturer today. They said clay with lots of iron oxide often causes scumming and recommended brown clay with less iron. I will let you know if the recommended clay will cause less scamming.

I get this scumming on a white body, not evident to the eye till glazed and only comes through one glaze that I use, fired to C03. this scumming can appear on the pots a number of days after firing.

A wipe with vinegar at bisque stage helps but not a total cure,  Have to hang onto pots some time before moving them on.

This only started occurring when the clay supplier moved interstate and presumably now uses materials from a different source. A beech indeed. 



#23 Pres

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Posted 06 June 2014 - 08:32 AM

Your water does not have salt in it when using a water softener powered by salt. It is about the ions in the water shifted using salt as a catalyst.

 

"Water softeners operate on a simple principle: Calcium and magnesium ions in the water switch places with more desirable ions, usually sodium. The exchange eliminates both of the problems of hard water because sodium doesn't precipitate out in pipes or react badly with soap. The amount of sodium this process adds to your water is quite small -- less than 12.5 milligrams per 8-ounce (237-milliliter) glass, well below the standard set by the Food and Drug Administration for "very low sodium"

 

http://home.howstuff...question991.htm

 

All of that taken in to account, does the small amount matter to clay, or say even watercolor, or other types of work where water is a component? I don't know, so maybe experimentation is needed here.  As I have said in other posts, I found that water effected the color intensity and life of paint in watercolor. I don't know what I was doing wrong or right, but that changing from tap to bottled water worked.


Simply retired teacher, not dead, living the dream. on and on and. . . . on. . . .                                                                                 http://picworkspottery.blogspot.com/


#24 Isculpt

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Posted 07 June 2014 - 12:26 AM

Pres,

 

oh. :blink:

 

Jayne






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