Insulating firebrick: a lightweight, highly porous brick, roughly 0.5 to 1.0 g/cm3, that insulates far better than dense brick while still standing up to direct heat. In US practice IFB is sold by group number, where the number times 100 is the rated temperature in degrees F, so group 23 is for 2300 F (1260 C) and group 26 for 2600 F. It is easy to cut and carve but weak, so it goes behind hard brick or in kilns with clean atmospheres.
Back the hot face with a course of IFB 23, it'll cut the shell temperature in half.
IFB soaks up water like a sponge. Keep it dry, and give any brick that got wet a slow dry-out of its own.
Also heard as
- insulating firebrick
- insulating brick
- 23 brick
- 26 brick
Do not mix it up with
- Hard brick: IFB trades strength and slag resistance for insulation; hard brick does the opposite.
Related terms
Soft brick
Shop and kiln builder name for insulating firebrick, light enough to carve with a hand saw.
Hard brick
Shop name for dense firebrick, as opposed to lightweight insulating soft brick.
Thermal conductivity
How readily a material conducts heat, the number used to size lining layers and predict shell temperature.
Ceramic fiber
Wool-like high-temperature insulation spun from molten alumina-silica, sold as blanket, modules, board and paper.