Homemade Fire Brick Experiments

[JohnMaguire]

Hello all!

I am making refractory bricks for a kiln I'm working on. These are going to be pretty standard hard/heavy bricks.

Researching the composition and other fire bricks got me interested in experimenting with making soft fire bricks. I'm planning to make three experimental bricks right now:

1. Two parts perlite, two parts high alumina clay, one part pure silica sand

2. Two parts sawdust, two parts high alumina clay, one part pure silica sand

3. Two parts crushed charcoal, two parts high alumina clay, one part pure silica sand

For each, I plan to do an initial firing up to 500 to 800 F to burn out the organics safely, then a second high temperature firing.

Has anyone on here made any attempts at homemade soft fire bricks? Do you guys have any suggestions on how to make them? What do you think of the experiments above?

[liambesaw]

If you're going to fire them in an electric kiln I'd skip the charcoal chunk experiment because it's gonna be pretty hard on the elements.

[Mark C.]

You need to study up a bit on this and you will find some better recipes .I have read about them before but I read a lot -maybe studio potter  mag in the 80s? Clay art for sure -you can search that forum easy.

in this link you can see the alumina content of various k factor insulating bricks like K23 k26 k 28 etc

There has ben a bit already done on this read some old clay art posts as well. I have a friend who years ago made hardbacks (I have one)

I do not think you need to twice fire them only one high temp fire . The burn out material is a key factor. Charcoals I would pass on.The sawdust maters as to what size it is.

[Mark C.]

One last thought -if you notice in a k23 soft brick its riddled with holes vs a k26 or a K28-as the number goes up -hotter face temperatures and better resistance to long term cracking and spalling from high heat areas. The holes are not noticed. Even in a K26 the brick seems voidless. I do not think you said what temp brick you wanted to make? 

So the less burn out voids the brick is more dense and will withstand  hotter temperatures

[JohnMaguire]

23 hours ago, Mark C. said:

One last thought -if you notice in a k23 soft brick its riddled with holes vs a k26 or a K28-as the number goes up -hotter face temperatures and better resistance to long term cracking and spalling from high heat areas. The holes are not noticed. Even in a K26 the brick seems voidless. I do not think you said what temp brick you wanted to make? 

So the less burn out voids the brick is more dense and will withstand  hotter temperatures

Thank you for the good info! Especially for helping point me to more in depth information and the past experience of others.

Part of the goal is to experiment. Even a deliberate failure can be useful, so I could see why one method failed versus another.

Since I'm using a gas kiln, is there any particular reason to avoid charcoal?

Do you think the less visible holes are due to smaller holes or just less voids in general? How could they achieve such light weight insulation with fewer voids?

I can definitely see smaller voids giving better strength and durability, though.

I'm not shooting for any particular temperature rating. I want to see what works in general as I'm not using them for a project.

Thanks again! 

[Mark C.]

I assumed you where using gas kilns. Charcoal shoukd be ground into fine pieces. When it large it can make for a mess in kilns with pots.

I have seen it mess up glaze fires a few times.Those were cone fires

I would  think the sawdust is easier to control size of particals than charcoal? maybe not?

[JohnMaguire]

Sawdust is easier to get everything a consistent size: a certain blade cutting certain woods will make every particle very close in dimensions to every other. Charcoal, though, can be made much finer and consistent. Just smashing it with a mallet in a bag could produce small -- if somewhat inconsistent -- particles. A roller ball mill could make very consistent sizes. I wager you could buy charcoal that's been through a mill, since it's a key ingredient in gunpowder.

I might try out crushing charcoal to different sizes for some different tests.

 

[Bryan Johnson]

Crushed walnut shells have been used.

[Alyosha]

How are the experiments going ? What about lime,alumine and vermaculite ?

[neilestrick]

5 hours ago, Alyosha said:

How are the experiments going ? What about lime,alumine and vermaculite ?

John hasn't posted here in quite a while, but if we tag him @JohnMaguire he might respond...

[Alyosha]

Thanks neilestrick