Spots On My Bisque

[dawilsoniv]

I am getting spots on my bisque that are faint but noticeable.  The spots look like something did not burn off completely or its iron traces and they are basically the color of rust or reddish brown.  I am currently firing at cone 6 in an electric kiln.  What am I doing wrong and can it be corrected?  Thanks.

[neilestrick]

You are bisque firing to cone 6? Do you mean 06?

 

Looks like maybe it was too close to the elements. Does the dark area take glaze as well as the rest?

[dawilsoniv]

Yes cone 06.  I cant tell you on the glaze because i make bisque only at this point and time.

[dawilsoniv]

The slip I make is basically one part ball clay kt14 to two parts talc, soda ash and sodium silicate.  I had considered that some stuff was not burning off completely and that was my first thought when I saw the marks.  Can the bisque I fired at 06 be fired again at a hotter fire?

[hershey8]

I recently did a bisque fire to 04 and found white areas in the bottom of my bowls. I may have stacked other ware inside the bowls, they were all made of the same type of clay. Clay supplier said that this happens sometimes, but that it didn't usually affect the final glazed product. I still wonder why it happens though. It happens only on the bottom...inside and out. This clay should bisque a pinkish to light terra cotta color. I don't understand the white part. Any thoughts?

[Davidpotter]

i get similar blotches when i rinse my bisque. but usually more yellow. for me its from the minerals in the hard water but doesn't seem to affect my glaze at all