Fire brick identification

[Jfeldman]

I have a large amount of firebrick I got from a friend that got them from a job site left over from a large industrial glass kiln. The bricks have never been used.
I have read that there are bricks out there that are meant to never cool down, or they will break. How would one go about identifying such a brick?

[UtahBeehiver]

Coming from an industrial glass kiln that most likely these bricks will be "super" duty and are very hard to cut and you will go through a lot of blades. I used super duty on my build, they were surplus from a steel mill which I suspect never cooled down either. I have never had a brick crack from thermal cycles.. They are very high in alumina (60%) which contributes to the hardness of the brick. Test cut a brick on a wet saw and if slow cutting they are super duty. Need to weigh the cost of regular fire bricks vs super duty vs blade cost. That said, I went for a super tight mortar joint on all faces, hence lots of cuts/blades. If I were to do this again I would focus on tight joints on the interior of the dome only and let mortar be my friend on the other parts of the brick joints.

[Tscarborough]

And use low duty for the floor.

[RandyJ]

I also used a combination of high and super duty to build my dome. I did not go for super tight joints through out. Just tight on the inside. I went through 2 rigid brand segmented blades at 65 $ each. I did use low duty on the floor. Everything is holding up nicely so far. If you can get a deal on the bricks I say use them.

Randy

[david s]

Make sure you use dense firebricks not insulating firebricks. If they're really light they are IFB's. Dense firebricks are a similar density to solid house bricks.

[RandyJ]

Yes I believe that a 2.5"x4.5"x9" brick is in the 7.5# range depending on brand and duty rating.

Randy

[Novaslo]

Coming from an industrial glass kiln that most likely these bricks will be "super" duty and are very hard to cut and you will go through a lot of blades. I used super duty on my build, they were surplus from a steel mill which I suspect never cooled down either. I have never had a brick crack from thermal cycles.. They are very high in alumina (60%) which contributes to the hardness of the brick. Test cut a brick on a wet saw and if slow cutting they are super duty. Need to weigh the cost of regular fire bricks vs super duty vs blade cost. That said, I went for a super tight mortar joint on all faces, hence lots of cuts/blades. If I were to do this again I would focus on tight joints on the interior of the dome only and let mortar be my friend on the other parts of the brick joints.

I too went through two blades on the Forno Bravo bricks that I bought. I believe they are medium duty. They cut well but we're not easy to cut. Not light either. Middle of the road is what I would say they were.
I also went for tight mortarless inner joints with plenty of mortar on the outside or inside. I used a mortar bag to squirt mortar into all the joints. I have had zero problems and the whole oven is very solid.

The only change that I would make would be to insulate the floor a bit more. I have 2 inch fiber board as my floor insulation and I would say that I am worried more about cooking the top of my pie rather than the bottom. I will burn the bottom if not paying attention.

[Tscarborough]

I am pretty sure they use Whitacre-Greer which are low duty.