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Posted by Bill DeWitt on July 24, 2006, 8:17 pm
Please log in for more thread options
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
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Posted by Steve Mills on July 25, 2006, 6:47 am
Please log in for more thread options 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
>
> 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
>
>
--
Steve Mills
Bath
UK
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Posted by Bill DeWitt on July 25, 2006, 7:34 am
Please log in for more thread options Hi Steve...
>
> That sounds very much like the stuff used normally for fireplace
> setting.
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.
> 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.
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...
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Posted by Steve Mills on July 25, 2006, 6:58 pm
Please log in for more thread options >Hi Steve...
>
>>
>> That sounds very much like the stuff used normally for fireplace
>> setting.
>
> 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.
>
>> 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.
>
> 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...
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
--
Steve Mills
Bath
UK
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Posted by Bob Masta on July 25, 2006, 8:54 am
Please log in for more thread options On Mon, 24 Jul 2006 20:17:46 -0400, "Bill DeWitt"
>
> 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
>
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
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator
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