Picking a firebrick

[Tejaycar]

Trying to decide between two bricks.

https://www.fornobravo.com/pompeii-oven/brick-primer/ suggests silica of 38.

Duty	Low	Medium	High
Alumina (%)	30	38	50+
Density (lb./cu/ft.)	127	135	150
Service Temperature (F)	2350	2450	2650

I have local sources for Smithfield medium duty https://www.alsey.com/s/PDS-Smithfie...-Firebrick.pdf and Jet DP high duty https://www.alsey.com/s/PDS-JET-DP-H...-Firebrick.pdf From what I've seen, the medium duty is the way to go, but in this case the medium duty is 30.8% Alumina, while the JET DP is 37.6%

So going on the stats, it seems the high duty might be better here? Both have very similar bulk density at 130.2 and 133.7 respectfully.

Any thoughts on this?

[Chfrob]

question about firebricks, I was only able to find the half bricks so they are thinner than the regular firebricks, was planning on just lining the inside of the oven with them and use the regular clay bricks for structure... any thoughts on this?

[Tejaycar]

It's an interesting thought Chfrob . The lining of fire bricks would help prevent spalding, and the clay bricks would probably provide decent mass, so I suppose it could work. How would you get the structure of the "lining" stay put though?

You could always use the splits the same way as full-size bricks, you'd just have twice as many courses.

[Petter]

Use medium or low duty. High duty burns the bottom more easily. Using low duty shortens baking time since it allows you to bake at higher temperature. This applied to bread too. When I bake bread, I use 30 mm high duty in the home electric oven and I can't go above 250 C, or I'll get burned bottoms. High duty firebricks also wear the diamond cutting blade a lot faster. They all cut well though.