Spot On Bisque

[Roberta12]

I had about 50 mugs in the kiln.  Bisque load, speckled buff, Laguna, fired to 04.  There were 3 mugs that had spots like this on them.  It's almost pitted.  It looks like iron or something.  Any thoughts?

 

Roberta

[Mark C.]

looks like an iron burn mark. 

[Min]

Laguna clay from their California plant can have lots of crap in it. I've pulled out matchstick size pieces of wood, metal bits, and small bits of plastic. Maybe from this?

[Roberta12]

Laguna clay from their California plant can have lots of crap in it. I've pulled out matchstick size pieces of wood, metal bits, and small bits of plastic. Maybe from this?

could be.  It looks like iron to me.....this spot is the largest.  This is the last of this particular batch.  Let's hope the next 300 pounds is better. 

[Mark C.]

My helper just found a piece of wood that was about 2 inches x1/2 inch in our porcelain from Laguna.

When you go thru many tons per year its always going to turn up some crap. Iron burn outs are common in my past 40 years.

You can grind it out with a dremial then patch 

[Roberta12]

Now that I think about it, when I was using Laguna's Bmix, I would get a box or two that had fairly large rocks in it. 

 

Thanks all,

 

r.

[Marcia Selsor]

I have seen those specs before. I agree it is an iron spec. I don't think a piece of wood  would leave a make like that at bisque temp.

Marcia