Do You Cook Directly on the Firebrick? Other options?

[pizzagary]

I reached out to the place where I buy my medium-duty firebricks from and asked if they know if the firebricks I'm using are safe to cook directly on. The answer I received said that while they know most people who build pizza ovens with them do cook directly on them, they are "not food rated at all".

Do you all cook directly on them? Any of you choose different materials to use as a cooking surface?

I have already laid the cooking floor with firebrick, but I could put a cooking layer (of something) on top of it. I was thinking maybe of getting some cordierite baking stone tiles and cutting them to fit in my 30-inch diameter cooking surface. So expensive though.

[JRPizza]

I think you will find that pretty much everyone that has a brick floor and cooks pizza does it directly on the floor. There are folks that use pans but that is usually for speed like when serving a large party or making gluten free crusts to avoid any contamination risks from residual flour on the cooking area.

[SableSprings]

Gary, I hate to ask this but it looks like you don't have any insulation between your cooking floor bricks and the supporting concrete top slab. Fairly critical issue if that's the case. Also having weep holes in the top slab and a mosaic tile moisture barrier/channeling beneath the insulation are very important additions if this oven will be out in the elements... especially Minnesota!

[JRPizza]

Ugh yeah, like Mike said having the floor bricks in contact with your concrete hearth will make it close to impossible to maintain proper cooking temperatures. What you want is a shell of thermal mass surrounded by insulation, so it will heat up relatively fast and cool relatively slowly.

[pizzagary]

Sorry for the late reply to everyone! Just to follow up, the photo I shared from 2024 was back when I was constructing it. The firebrick base is actually on special insulating concrete underneath and the rest of the dome, now fully built and finished, has a layer of insulating concrete, ceramic fiberglass, another layer of insulating concrete, all-weather concrete, and finally a layer of stucco. I fired my first pizzas finally (almost two years later) and I have been cooking directly on the firebricks, but I may eventually switch over to some food-safe tiles or stone since these firebricks have aluminum in them.

[david s]

Sorry for the late reply to everyone! Just to follow up, the photo I shared from 2024 was back when I was constructing it. The firebrick base is actually on special insulating concrete underneath and the rest of the dome, now fully built and finished, has a layer of insulating concrete, ceramic fiberglass, another layer of insulating concrete, all-weather concrete, and finally a layer of stucco. I fired my first pizzas finally (almost two years later) and I have been cooking directly on the firebricks, but I may eventually switch over to some food-safe tiles or stone since these firebricks have aluminum in them.

I would be very interested to learn of any firebricks containing aluminium and any reputable study that shows it is dangerous to human health. Fire bricks contain both silica and alumina (not aluminium) but both are in forms that are not harmful to ingest. Aluminium hydroxide is a naturally formed component of the heterogeneous clay body used to form the bricks which are then fired to high temperature to create the permanent brick The process of raising the temperature to over 1200C begins the process of vitrification which essentially begins to melt the silica, turning it into a glass. This process locks in all the chemical components permanently. Likewise for silica. The fine silica dust, created when dry cutting a fired fire bricks is dangerous to inhale because the fired particles are sharp and the silos in the lung lining has more difficulty expelling these minute shards whereas unfired clay dust presents far less of a problem. The smoke you might breathe in from the wood fire is probably more dangerous. But fired or unfired clay dust or the odd skerrick of wood ash is harmless to ingest. Humans have been firing clay, containing aluminium oxide for eons to make pottery on which we eat our food.
Any pathogens present on the firebrick surface are dealt with by the high and sustained temperature of the fired particles which is transferred to the bricks.
Firebricks are a safe cooking surface, unless you can prove otherwise.