Firebrick Test

[blacknoir]

ok, I found ANOTHER guy who has some firebrick he wants to sell. This one says he bought it from a local school a while ago but doesn't want it anymore. The problem is he has no idea what kind it is or what it was used for. Anyone know of a test I could perform to try and identify the brick?

Thanks,
Shay

[blacknoir]

From what I can tell an Insulating brick should be about 2lbs while a High/Medium/Low duty will be about 8lbs so it should be easy enough to distinguish between those 2 types. But, the next question is how do I distinguish between High, Medium and Low duty? Is it low that weighs 8 while Medium weighs more and High weighs more++ ? Google is a bit unclear on this topic..

[brokencookie]

For building an oven, it does not make a whole lot of difference. Low, medium and high duty bricks will all work fine. The only difference is that the higher duty bricks can take longer to heat.
Try to find out what kind of service these bricks were used in. If they were in a fireplace, they are almost always low duty bricks. In a school furnance, they would probably be meduim. The only time you find used high duty bricks is from industrial applications like blast furnances.
Schools are built by the low bidders. I am willing to bet that these are low duty bricks.

[blacknoir]

The guy had no idea what they were for. I'm really hoping you're right and they're low duty, I really don't want high duty in my oven. I'm tempted to save these for the fireplace and get different for the oven.. I'll see what they're like when I pick them up.

[RTflorida]

If they are dense high duty, they should weigh inexcess of 9 lbs each. It is the low and med bricks that weigh somwhere in the 8 lb range. This is based on the size being 2 1/2" x 4" x 9". You really would not have any noticable issues using the low or med, it is the heavy duty that could up your wood needs (will take longer and more wood to get up to pizza temps), if you are a baker you will appreciate the added heat they hold.....when they get hot, they get very hot and are slow to release all that heat.

[dmun]

High duty bricks are also somewhat harder to cut. A low duty firebrick will cut much more easily than a red brick paver, a medium, about the same, and a high duty brick will be more like cutting hard stone.

You can run a test on your wet saw, and be pretty sure which one you have.