does %alumina in fire bricks really matter?

[johnnybrewmeister]

I know FB plans/kits specify 38% alumina for medium duty bricks, and 30% for low duty bricks. Looking loacally (San Diego, CA) I'm finding only 20-28%, and most sellers have no clue (and I have to talk to the manufacturer).

So if I used the low-end 20% bricks, what does that mean...would the oven heat up to temp sooner (using less wood), but not hold the heat for longer extended cooking times? Can better insulation make up for lower alumina content?

I'm looking to cook pizzas, then breads, and an overnight slow cooking session would be desireable.

Thanks for any info,
John.

[Gulf]

Re: does %alumina in fire bricks really matter?

Johnny,

The vast majority of the homebuilts on this site are made from low duty firebrick. That is the grade that is required for residential fireplaces. So, it is the grade that is stocked in most brick yards. And, like you have found out, most salesman don't have a clue.

You will be just fine with the brick that you have found imo .

[johnnybrewmeister]

Re: does %alumina in fire bricks really matter?

Thanks for the info. I was hoping that was the case.
I wonder how many folks on this forum even paid attention to the alumina content of their bricks?

It seems to me if you insulate well, it should be fine.

John.

[david s]

Re: does %alumina in fire bricks really matter?

Don't get hung up on alumina content as a sole measure of a firebricks suitability. There are many other factors involved like density, degree of vitrification and porosity. Firebricks manufactured will vary from brickworks to brickworks, but generally any firebrick designed for fireplaces will be suitable.