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differences in bricks for oven?  RSS feed

 
Leah Sattler
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since there is tons of construction around me  I have access to lots of bits and pieces as well as whole bricks that are leftover from facing houses. Could I use these to build and oven? do they need to be special to withstand high temps and repeated heating and cooling?
 
Leah Sattler
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anybody read this? http://www.amazon.com/Forgotten-Building-Using-Brick-Bake/dp/0911469257
 
paul wheaton
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What you want is "fire brick".  It tends to be lighter in color and have shiny specs in it. 

Fire brick can handle really high temperatures and is often used in the immediate firebox. 

Regular brick can handle pretty high temperature and is usually used for the everything in a fireplace except the immediate firebox.

 
Leah Sattler
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thanks for the info. Somewhere in my cobwebby brain I thought there was a difference. There are quite a few homes going in that have fireplaces, both indoor and out so I have a chance at getting some bricks appropriate for the fire box.
 
Dave Boehnlein
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I'm not the one who designed it, but we have an earth oven with a brick cooking surface. We used normal bricks (not fire bricks) for the cooking surface because someone told us that fire bricks would heat up too much and burn the food. We dry set the bricks so we could easily replace them if they started to disintegrate.

Dave
 
Ken Peavey
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I'm a foreman for a refractory contractor.  Among the many things we do is install firebrick in industrial settings.  Thought I'd offer up a primer on the subject...

Regular house brick is made out of clay with or without sand.  There are lots of different styles and colors but the things are made from clay heated to 1800-2000 degrees until the particles vitrify, that is, they almost turn into glass but not quite.  This is what gives them the strength to be stacked 10 stories high.

Firebrick is produced using alumina and/or crystalized silica.  The method of production is similar but at a higher temperature because of the material involved.  The alumina content is what makes firebrick so special.  When brick gets hot it expands.  House/clay brick does not heat evenly-one side will be hot, the other will be cold.  The result is thermal fracturing as the hot side expands and breaks off from the rest of the brick.  Dave did well to dry set his brick because of this.

Alumina has a high rate of heat transfer.  The flame hitting one side of a firebrick is able to move through the brick quickly.  The brick heats up evenly, avoiding the thermal fracturing.

There are all sorts of different grades of firebrick for all sorts of different uses.  For home use, the firebrick sold at stove shops is usually rated for 1800 degrees which will handle every need you can come up with for your home fireplace, woodstove, brick oven, bbq, smoker or what have you.  They will run you $3-5 each.
 
Jocelyn Campbell
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Great info kpeavy. You might be the one to ask a question that's been nagging at me since I took a Cob Cottage Pyromania (rocket stove) workshop early this year.

One of the instructors there said that the older house bricks--say, from the 1950/60's or before--were made better and are therefore less prone to thermal fracturing. I think he even said he prefers using old clay bricks to using firebricks in the hottest parts of his rocket stoves.

Could the older bricks be that much better? Would the older house bricks possibly have less sand? If not less sand, what could make them sturdier in high heat situations?
 
Ken Peavey
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I have no answer for you.  Before WWII, bricks were produced in hundreds of different locations just in the US.  Each foundry would have their own recipe and procedure.  Post WWII industrialization has left many of the smaller brick producers in the dust, some of the clays have been mined out, some of the old recipes and methods lost to the ages.

For something like a rocket stove, try different bricks, see what works best for you.
 
                          
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the sillica in fire bricks could be replaced with powdered glass
clay & powdered glass & heat = fire brick

cement mixer & large steel ball bearings/ hard rocks & broken glass = powdered glass
 
Len Ovens
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fire bricks are better.....maybe. fire bricks do handle the heat better, but water not so good. the standard clay brick will actually handle water sprays a little better than fire brick. Many brick ovens have been made with red clay brick and some have lasted a long time.... like since before gas or hydro where around. Fire brick is relatively new.

Len
 
Joel Hollingsworth
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Bird wrote:
the sillica in fire bricks could be replaced with powdered glass
clay & powdered glass & heat = fire brick

cement mixer & large steel ball bearings/ hard rocks & broken glass = powdered glass


There's quite a bit of sodium and calcium in most sorts of glass.

The recipe you're describing might result in something like Portland cement.

Clay typically isn't a source of pure alumina, and glass typically isn't a source of pure silica.
 
Ken Peavey
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Along with the brick, we should talk about the mortar.  Refractory cement is the stuff to use with firebrick.  Also known as refractory mortar, thermal mortar and high temperature mortar.  What sets this apart from run of the mill mortar is the silica content.  As with firebrick, this mortar can take the punishment of repeated heated and cooling.  Regular construction grade mortar will hold up for a while, but will crumble considerably sooner under the strain of thermal expansion. 

Refractory cement is considerably more expensive than construction grade mortar.  An advantage is that less is used.  A bond with 1/16 of an inch will be suitable for home applications.  Planning and preparation of the job will reduce waste.  Have your bricks laid out, as many cuts already made as possible, everything neat/clean/orderly and ready to go.
 
Larisa Walk
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We built a couple of masonry brick ovens/heating stoves using paving bricks for the interior fire box and decorative house bricks for the facing.  Paving bricks are high-temp fired and have a glazed appearance on their surface.  They are bigger than standard bricks, much thicker, and weigh about 9 to 10 pounds a piece.  If you can find old streets being torn up, the bricks are often land-filled and are free for the hauling.  House bricks should have their cores filled with mortar or sand if they're not solid bricks.  The trick for building a double layered brick stove is to leave an expansion joint between the 2 layers to allow for the temperature differential.  We used a sheet of cardboard to maintain the spacing while building - this is left in place and will eventually carbonize.  You definitely need refractory cement for the mortar in the firebox portion.  Regular mortar will suffice for the rest.

Larisa
 
solomon martin
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Walk wrote:
  You definitely need refractory cement for the mortar in the firebox portion. 


You can save money on refractory cement by using this mortar recipe instead (trust me, I'm a mason)

3 parts sand:1part portland cement:1part powdered fireclay

Refractory cement is great stuff, but hella expensive.  I does come in gallon cans though, so if your fire box is small it may be the way to go.
 
ronie dee
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Sol wrote:
You can save money on refractory cement by using this mortar recipe instead (trust me, I'm a mason)

3 parts sand:1part portland cement:1part powdered fireclay

Refractory cement is great stuff, but hella expensive.  I does come in gallon cans though, so if your fire box is small it may be the way to go.


So what is fireclay? A google search brought up only one tile called fire clay.
 
solomon martin
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fire clay is milled porcelain, sometimes mixed with a small amount of lime.  It comes in 50lb. sacks and costs less than 10 dollars where I live. (some places sell small amounts by weight) Gladding/McBean is the brand I most often use.  I buy mine at Mutual Materials which has regional stores all over the place.  You could also talk to your local ceramicist who would know all about the stuff.  It is often used to build kilns.

I have also used fire clay to make cob with, it is a light buff yellow and when used with white sand, lends itself really well to being dyed or colored.

Remember when using mortar to build a fire box that less is better.  You should use a butter knife to rake the joints with.

Good luck, and feel free to ask more...
 
Rich Pasto
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...
 
A Alexiev
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Sol McCoy wrote:fire clay is milled porcelain...


Does anyone know if this mixture for Refractory Cement is as fire-resistant to 2000?
3 parts sand:1-part portland cement:1-part powdered fire clay (milled porcelain)

Appreciate a reply.

Also, not sure of an outfit that sells milled porcelain online. If anyone knows of a source, please send a note.
Thanks.
 
jonathan Seethaler
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First off, you can buy fireclay at your local hardware store most likely. I know that the Home Depot near me sells it by the bag (probably around 50-80 lbs).

when I googled melting points for the different ingredients I found:
sand - melting point 1600C 2900f
Portland Cement - melting point 1200C 2200f
fire clay - melting point 1500C 2750f

assuming that the mixture is measured by weight I'm pretty sure that you can just average out the temperatures. (3*2900 + 2200 + 2750)/5 = 2730f
 
Michael Cox
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John,

Welcome to the forums. Just a heads up that the thread you replied to is very old, so the people in it are unlikely to be following it now.

Mike
 
jonathan Seethaler
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Ya, I know. However, since I realize that there aren't many good sources of information for this kind of stuff as I have recently looked for information I figured it might help some wandering soul in the future.
 
allen lumley
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Jonathon Seethaler : There is certainly nothing wrong with using an old thread as long as we all stay on topic!
I often send people with enquires on this topic to www.traditionaloven.com
Have them scroll down to the articles near the bottom ! For the Good of the Crafts ! Big AL
 
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