Ron-

I assume Gurke was talking about ash rather than ashes, that is the white, purely mineralized remains of burnt organic material. I assume there is some chemical effect from firing bricks with this stuff in the clay, but I have no idea how that would work.  I do know that fireclay used as mortar for the bricks in a smith's forge is supposed to have ash mixed in- perhaps for the same reason. If anyone out there knows about the chemistry involved, I'd love to hear an explanation.

Marty Pickands
New York State Museum

>>> Ron May <[log in to unmask]> 5/27/2007 9:03 PM >>>
 
In a message dated 5/17/2007 9:49:43 A.M. Pacific Daylight Time,  
[log in to unmask] writes:

What  kind of ash- coal ash or wood ash? Gurke, in his book Bricks  and
Brickmaking (U. of Idaho Press 1987), mentions that ash is  sometimes
mixed with clay to retard shrinkage and cracking while the bricks  are
drying


I cannot imagine organics surviving kiln firing of bricks. I have studied  
Mexican kilns in Baja California that created sandy bricks that trapped some  
organics in the core because oxygen hit the surfaces after the fuel spent out,  
but I do not recall seeing ash or plant remains in the black carbon streak.  
Higher fired kilns with oxidizing temperatures would strip all organics from 
the  ceramics. What purpose would ash serve under these circumstances?
 
Ron May
Legacy 106, Inc.



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