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-   -   First firing of cream hard clay bricks. (http://www.fornobravo.com/forum/f51/first-firing-cream-hard-clay-bricks-15964.html)

deevex 05-21-2011 03:06 AM

First firing of cream hard clay bricks.
 
Hi, I have misunderstood the process, I guess I studied in a differant enviroment to your wood fired ovens. I appoligize.

david s 05-21-2011 04:38 AM

Re: First firing of cream hard clay bricks.
 
Hi deevex,
Yes the 200 C and 500 C points are important, thectrouble is most oven owners want to get their ovens to temp as quick as possible, unaware of the chemical and physical changes. Also when using wood as a fuel it is difficultvto control the temp rise and with flame hitting the apex of the dome while the sides at the bottom are still cold there is considerable temp difference resulting in expansion stresses which are uneven. I always advise a slow heat up even after curing in order to be kind to the refractory, but reality determines folks desire to get it to temp as quick as possible. Many potters boast about how quick they can do a stoneware firing obviously oblivious to the changes taking place.

brickie in oz 05-21-2011 06:49 AM

Re: First firing of cream hard clay bricks.
 
deevex, you are talking about firing wet clay not firing the oven built with firebricks arent you?

GianniFocaccia 05-21-2011 10:04 AM

Re: First firing of cream hard clay bricks.
 
My guess is that its prudent to fire one's oven slowly, allowing time for equalizing rests at 100C (212F), 200C (392F) and 400C (752F). If time is a factor, total firing time could be shortened by using more wood (extending the ring) at each stage.

david s 05-21-2011 12:42 PM

Re: First firing of cream hard clay bricks.
 
Quote:

Originally Posted by brickie in oz (Post 113476)
deevex, you are talking about firing wet clay not firing the oven built with firebricks arent you?

The same applies to the clay content of the mortar. It is doubtful that you'd get all of the mortar up to 573 C , so it probably never gets truly "fired"

david s 05-21-2011 01:01 PM

Re: First firing of cream hard clay bricks.
 
This page is well worth reading
What Temperature Does to Clay - How Temperature Changes Clay

brickie in oz 05-21-2011 04:06 PM

Re: First firing of cream hard clay bricks.
 
Just read that page David, they are talking about wet clay being fired and not fired bricks being refired, or did I miss something? :confused:

Tscarborough 05-21-2011 04:24 PM

Re: First firing of cream hard clay bricks.
 
The processes he describes have already happened in a home built oven. After initial firing and cooling (at the brick plant), the coefficient of expansion for both fire clay, fire brick, common or even facebrick is very small.

brickie in oz 05-21-2011 04:28 PM

Re: First firing of cream hard clay bricks.
 
Thats the way I read it too.
The thread is confusing and makes you think its the fired brick doing the weird and wonderful things everytime you fire the oven. :(

david s 05-21-2011 04:43 PM

Re: First firing of cream hard clay bricks.
 
Quote:

Originally Posted by david s (Post 113483)
The same applies to the clay content of the mortar. It is doubtful that you'd get all of the mortar up to 573 C , so it probably never gets truly "fired"

I was actually referring to the clay in the mortar which has not been fired.


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