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david s 05-16-2011 02:56 AM

Brick porosity
 
I did a test of the brick porosity of one of my firebricks yesterday. The brick was 12"x 9 1/4" x 3" and weighed 9.25Kg dry. Soaked for 24Hrs it weighed 11.5 Kg which is approx.20% I did not remove moisture from the dry brick first and my old spring bathroom scales are not too accurate but it indicates that the brick has taken on a lot of water. This indicates that the brick is very porous and not very vitrified. This quality is desirable to make the brick highly refractory but undesirable in that it will absorb water easily and hold a large quantity. I have read that it is the moist heat that is the WFO's secret, so perhaps the porosity of the bricks is an important factor in the WFO's success in cooking superiority.

brickie in oz 05-16-2011 11:51 PM

Re: Brick porosity
 
Slow day at work was it? :D

david s 05-17-2011 01:35 AM

Re: Brick porosity
 
No, flat out actually, but it is a topic I've been getting interested in and was hoping someone else might might chime in to give some constructive input into the subject so we can all benefit from increased knowledge. And weighing one brick is way easier than cutting lots of them.

brickie in oz 05-17-2011 02:10 AM

Re: Brick porosity
 
Quote:

Originally Posted by david s (Post 113174)
And weighing one brick is way easier than cutting lots of them.

Why are you cutting lots of wet bricks? :confused:

david s 05-17-2011 02:39 AM

Re: Brick porosity
 
I didn't say I was.

david s 05-17-2011 03:14 AM

Re: Brick porosity
 
I agree, but is it the fuel used or the porous bricks that give it that superiority?
I think also that a WFO cooks with radiating heat rathe than by convection like a standard oven.
Maybe someone with experience with both a steel dome and a firebrick dome may chime in. Although a steel dome with a firebrick floor is still half a firebrick oven.

Tscarborough 05-17-2011 05:38 AM

Re: Brick porosity
 
The ones we carry give a rated porosity of 13-17%.

http://www.wgpaver.com/files/PDF/Fir...heet%20Red.pdf

david s 05-17-2011 02:31 PM

Re: Brick porosity
 
Thanks Tscarborough,
Given the high degree of porosity of fire brick, presumably some containment of water, rather than full saturation, in the brick when laying them is desirable to reduce the tendency of the brick to suck water out of the mortar too fast. Is this a logical conclusion?

Tscarborough 05-17-2011 04:26 PM

Re: Brick porosity
 
Yes, as I have stated a dozen times, the proper amount of water is SSD. Saturated, surface dry. That is to say, the surface will not have a sheen, but it will be damp. Usually, a dip before use is adequate, but in hot (like yours and mine hot, 95+ degrees) and windy, you may have to either soak them and then allow them to dry a bit before use, or, as recommended by the BIA, hose the pile every now and then.

As an FYI most common brick have less than 5% absorbtion, and hard fired face brick are usually far less than 2% in a 24 hour soak test.

david s 05-19-2011 04:39 AM

Re: Brick porosity
 
As an FYI most common brick have less than 5% absorbtion, and hard fired face brick are usually far less than 2% in a 24 hour soak test.[/QUOTE]

I wonder then if this would explain why firebricks are considered the superior cooking brick, with more porosity and their ability to store more moisture, are the preferred choice over common reds?
Or is it their greater ability to withstand thermal shock?
Or doesn't the difference really matter?


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