fire brick quality

[limey1usa]

Could somebody please advise me.
Have started my first oven, after was given a pallet of fire bricks. After pouring the base i was advised that furnace fire bricks are not suitable for wood fired ovens.
Am i wasting my time using these bricks or are they ok just not the prefered choice

[Stevenb]

Re: fire brick quality

I would research and see if you can find the alumina content. That and the weight seem to be the big factors. I have built two with alumina content on 29% and a weight of 7-8 lbs each. They hold heat so good it is amazing. good luck.

[dmun]

Re: fire brick quality

Firebricks from the firebox of a boiler or furnace should be OK. The ones you want to watch out for are ones that were used in blast furnaces or smelters, that might be contaminated with heavy metals.

[limey1usa]

Re: fire brick quality

Thanks for the info,the bricks are brand new well they are old but never used. They are stamped 60 hw which i think means 60% alumina .but i have been wrong before.

[cobblerdave]

Re: fire brick quality

Wow thats a find.... mine are 29 per cent... lite duty and work like a charm so those puppies should hold some heat

Regards Cobberdave

[Johnny the oven man]

Re: fire brick quality

Thanks for the info,the bricks are brand new well they are old but never used. They are stamped 60 hw which i think means 60% alumina .but i have been wrong before.

Yep, 60% and made by Harbison Walker. Good find.

[pinchpotter]

Re: fire brick quality

Hey first post here... I'm a potter and am very familiar with the atmosphere that comes about when you fire a kiln up into higher temperatures. This is a natural part of firing pottery. Most glazes for pots have oxides in them used for coloration or melting. These get vaporized literally becoming the atmosphere of the kiln and that gets sucked directly into the pots but also the bricks lining the kiln. Lead glazes have lead oxide and lead vaporizes at around 1600 degrees f. Anytime you hit that temperature in a contaminated kiln; out will come that same remnant atmosphere. The fire bricks are able to literally absorb this atmospheric gas and it' pretty much stays there. The process of reduction firing basically the manipulation of the kiln's atmosphere so you can get just the right dirtiness from the gas and smoke and that adds an overall effect to your clay body color and glaze qualities. So you also want to buy bricks that haven't been reduced by the kiln atmosphere. They are literally cleaner, so to speak.

So what I'm saying is...It's not good to use any brick that you know has been fired in an industrial process that's gone up over 1800 degrees multiple times but you don't know what was actually being fired and then expect to do anything with food near it. Also many of these firebricks are made of fire clays that are high in sulfur, these will off gas trace but toxic amounts directly into the atmosphere of the oven when a certain temperature is reached and with sulfur that temperature is actually quite low.

Then there's the obvious one...some fireclays have alot of sulfur in them, definately don't buy those. An example is if you tried to use roseart fireclay from Ohio it might kill ya. I'd look for the AP greene fireclay from Missouri. All these fireclays have a mine name which signifies it's origin and you can get some basic specs before you buy. There's thousands of different mines all over the world you just need to figure out what the properties of the local clay are. If you dig your own clay, try safely test firing a dry one pound batch up in a well ventilated kiln and sample (smell) what get offgased when it gets pretty high in temperature. If you go that you can also check the clay shinkage rate with a simple potters test (google it). Understand tho...if it is offgasing sulfur that means you are dealing with vaporized sulpheric acid and if strong enough you could fry your lungs very easily. All this stuff is basic industrial materials and many are exactly safe for the home crafty type person.

[Datadawg]

Re: fire brick quality

Wow, this sounds fairly ominous. I wonder if there are pizza ovens out there oozing some nasty stuff onto the pepperoni...