Super Duty brick?

[redcabinsteve]

On marketplace super duty is offered at a big discount. According to Guide SD is 60% or so. Looks like the Clipper SD is 42%. The seller has 2-3 different bricks of different manufacturer. Any idea why the 42% would be a poor idea? First post, fabulous stuff here.

[Gulf]

42% Alumina is doable imo. But, have you compared the "discount" to low duty fire brick? And may I ask what is the price of both in your area?

[redcabinsteve]

Joe, the price is $1. The guy has 900 of them. He is in Gatesville, Texas and he's on FB marketplace. Although the alumina content would probably be ok I will pass because of another post. That post said his super duty brick were so hard and difficult to saw thru the number of trashed saw blades negated any savings. I'm going to stick with the program.

[Gulf]

The terms light, medium, and super duty can vary among distributors. Especially the use of the term "super duty". I have had experience using 70+ alumina brick. I would definitely agree that 70+ are too hard to work with. Did the discussion, you reference, state the actual alumina content?

[redcabinsteve]

Gulf, sorry I see now the spec image doesn't show up well on the forum.

Composition 2.3% TiO2, 52.6% SiO2, 42.2% Al2O2
Max Operating Temp 3187 F
Cold Crushing 6300 psi
Apparent Porosity 15.3%

[redcabinsteve]

Gulf, a local large masonry supply place near me has standard size firebrick in stock at $2.70 each. They know they’re rated at 3000F and that contractors use them in fireplace construction. For alumina content they’ll have to call the manufacturer. I thought they were more like $5. If it’s the right stuff I should grab it.

[Gulf]

Firebrick rated for residential fireplace construction is probably more closely governed than any other refractory brick. They are the lowest dense firebrick in alumina content. However, they will perform just fine for a WFO. From which, that is what the majority of the ovens on this forum are constructed. In my area, I saw low duty firebrick jump in price from around $1.85 to $2.15 each last fall. No doubt, that what you are seeing is about the going price due to the economy. I haven't match priced brick since then.

If the brick yard can give you the name of the manufacturer, you can research the material data sheet yourself.

In any situation, low duty is what I recommend for the oven floor. I was only trying to clear up the differences in alumina content which is relative to the hardness of firebrick.

70% alumina is a a "no go" but, 42% should be "doable" for the dome if the price better fits your budget imo. As always, it's your call.