My Brick is Bigger Than Your Brick!

Brick size may actually matter depending on what temperature you're trying to fire to. Firebrick, or soft brick as they're called, come in either 2 1/2in or 3in thickness. Check what size your brick is by measuring the ledge of your kiln like in the pictures below.


If your firing to cone 10 or even cone 5, I'd recommend getting a kiln that has 3in brick. It provides 1/2in of extra insulation around the whole kiln, although it doesn't seem like much, it actually makes a difference.

If you're firing to cone 05 for the most part or cone 5 max, then 2 1/2in brick is just fine. At cone 5 using 2.5in brick, your kiln will be losing a bit more heat than if you were using 3in brick, but it will still get to temperature.

Personally, if I had a choice in my own studio, I'd use nothing but 3in brick kilns. Because although I glaze at 05 for the most part, it's nice to have the extra insulation in case I want to fire higher.

I should also mention there is no difference in strength between 2.5in and 3in brick.  They are both equally fragile, thus the name "soft brick."  The only difference is more insulation; for retention of heat in higher firings.