Fire Clay?

My local brickyard has bags of something called "Fire clay" which they instruct me to mix with portland cement to make a fire brick. I suspect that this is wrong (or useful only for fireplaces). My intuition tells me that I should form it into my shape (I have a special shape in mind) and then have it fired like regular clay.

Am I right? If I make a special shape with fire clay, then fire it properly, will I have a fire brick I can use? If so, what are the criteria for firing it properly? Any limitations or requirements or discussion would be welcomed! My web searches have not been fruitfull.

BTW, my wild clay turned out to be merely a sticky-ish dirt. No amount of firing short of melting it into glass beads would turn it into ceramics. As a glaze it is a pretty copper but completely undurable.

Thanks in advance, Bill

Reply to
Bill DeWitt
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Bill,

That sounds very much like the stuff used normally for fireplace setting. I used it for setting wares in a wood-salt kiln, for which it is excellent, however I can't get it down here in the UK any more which is a serious pain in the you-know-what. If you want to make fire bricks, mix just enough plastic stoneware clay to it to get it to hold together (actually you may not need to add anything) and fire to stoneware temperature.

Steve Bath UK

In article , Bill DeWitt writes

Reply to
Steve Mills

A later call to the owner of the brickyard suggests this is the case. He believes that the alumina level is in the 30% range I understand is needed for fire bricks.

Just to be certain, I believe you are saying that if I get a bag of this clay (a dry powder) I could moisten it, and if it is not plastic enough, mix a little stoneware clay -into- the fire clay, then fire normally (I understand it is a high ~2300f temp)? Or, as my reading hints at, are you saying that stoneware clay itself will make a respectable fire brick?

Thanks again...

Reply to
Bill DeWitt

I don't know about the Portland cement mix, but if you are trying to make firebricks to build a kiln, I suspect you would be better off just using the fireclay, but mixing it with sawdust or some other burnout material. This will give you an insulating fire brick that can withstand high kiln temperatures. Of course, only you can judge whether it is worth all the time and effort compared to just buying IFB. You may not find it at your local brickyard, but they can probably refer you to a place that has it. In my area (SE MIchigan, USA) I found that the best place to get IFB is not a pottery supplier but a place that works on industrial furnaces. You will probably have to buy it by the box (25 bricks), but that won't be a problem if you are building a kiln.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

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Reply to
Bob Masta

Thanks, I will probably try that.

I bought some firebricks, but want to make some special shapes so that I have a decorative kiln.

Reply to
Bill DeWitt

In article , Bill DeWitt writes

Your first interpretation is correct. Granular Fireclay is highly refractory and (usually) non-plastic, hence it is good for brick making as its fired shrinkage is much lower than plastic Stoneware clay. The latter does not make a good firebrick unless it contains as near as dammit 50 percent plus refractory material such as grog or sand. Like Steve Graber does with some of his clays, the addition of a certain amount of sawdust also helps as its burning out helps the insulation side of the mix. This is also true when using Granular Fireclay.

Steve

Reply to
Steve Mills

You might also want to check out the Clayart archives. There have been numerous recipes for firebricks and for castables. As I recall, there were even some exotic ones where you'd mix up the clay with egg whites or something to make a foam.

But it will be a lot of work. Depending on how decorative you want your kiln to be, note that commerical IFB is amazingly easy to cut and carve. (Wear a good respirator, or course!)

If you do end up making your own, please keep us posted on what you use and how well it works. Always good to have another tool in the mental toolbox for future project ideas!

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

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Home of DaqGen, the FREEWARE signal generator

Reply to
Bob Masta

Does anyone know what happens to cement blocks/bricks in a firing (pit fire for example)?

Reply to
DKat

Thermal shock gradually (or rapidly) disintegrates them.

Reply to
Bill DeWitt

his my help, but then again.

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Reply to
Leonard

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