Refractory brick or insulating brick

[wood11]

I am looking at building a wood-fired oven at home. I have sourced some 230x180x75 bricks that have been used on a kiln before, kiln located in Byford, Western Australia. The seller noted that bricks are not that heavy so I wasn't sure if they are a refractory brick or an insulating brick. Was advised that normal house bricks were heavier than this. I took one home and measured dimensions and weight to get a density of about 2000 kilograms per cubic metre. Is this a fire brick or an insulating brick? I have attached photo as well. Also I noticed that brick wears a fair bit after washing it down, not really spalling but small grains just coming off easily, didn't think it was the mortar since actual dimensions were a bit less than quoted 230x180x75. Would this be safe to use in the oven? Is there a life on these bricks? Kind regards.

[texman]

medium duty firebricks are heavier than any standard builder brick. My take on this question is always the same: if you put all this work into building an oven with inferior brick, you will not be happy with the money you saved. They do appear to be firebrick, but the weight and the slight spall would give me concern. In the end, i would hate to see you have to start over because of questionable materials or break a tooth on a chip.

[UtahBeehiver]

Insulating firebrick are commonly used in ceramic kilns. Although not good for the dome or floor they can be used as floor insulation under a the oven floor with good Insulating performance.

[david s]

The density of your bricks indicates that they're dense firebricks, assuming the brick was dry when you weighed it. They should be suitable and safe. Providing the price is good, I'd be using them rather than new bricks. Insulating firebricks would have a density of around 700 kg/ m3 (0.7 kg/ litre)

[UtahBeehiver]

I was responding from a phone and after seeing the pic I agree with David S on the brick being a firebrick and not an insulating fire brick (IFB) which can be easily scored or cut with a hand saw or knife. I understand how high the brick and material cost are for the southern hemi builders so like David said if you can get a good price, go for it.

[wood11]

Cheers thanks to all, especially david s.