Raw Glazing

[Whispering Grass]

Hello,

 

I am currently testing a glaze, with a view to using it as a raw glaze. It works well on my thrown stoneware bowls, however, keeps crawling (and previously blistering) on a black stoneware clay that I am using.

 

I am making pinch pots with the black clay , and using this glaze on the inside (for the black clay). I have summarised below the glaze ingredients. If the % of ball clay was too low I am assuming that it would not have worked well on the stoneware. Is it the iron oxide content in the black clay that is causing problems, and if so can I do anything to counter act that.

 

Any hints/tips on what I might be able to do in order to amend this glaze so that I can raw glaze my black pinch pots would be great!.

 

 

Nephaline Syanite 47

Whiting 7

Dolamite 16

Standard Borax Frit 8

Ball Clay 22

 

I have an electric kiln, and fire to cone 6 (6 hours to 650 degrees centigrade, then full to 1220 degrees centigrade, then soak for 20 minutes, then natural cool).

 

Its a lovely natural looking glaze on the stoneware, however, just isn't working on the black clay.

 

Thanks in advance !

[bciskepottery]

The black stoneware may contain manganese. What brand/name does the clay have, e.g., Standard 266. You can check the company website for an MSDS that lists contents.

[Whispering Grass]

thanks for that. I did check, and yes it does have .3%. Excuse my ignorance, not sure how that will affect the raw glazing process ?

 

Lorraine