#11  
Old 01-11-2009, 02:40 PM
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Thumbs up Re: Fire bricks versus 'Pressed Reds'

Adrian,
the ovens are only designed to reach say a round figure of 500˚C whereas a kiln can be required to go to over 1000˚C. I have a Ward Kiln that is used for ceramics and pottery which I use for annealing and firing ceramic inks on glass and pottery. The high fire inks are fired at 860˚C so the bricks need to be better than the common reds or in your case the creams.
Back to your ovens. If the brick is fired at over 1000˚C and is only going to achieve a half that, then it will perform OK.
As RT posted earlier, the thermal shock of continually heating these bricks from cold to baking temps over a 20 or 30 year period, say each week or fortnight, MAY show sign that a firebrick may not.
I would not use a brick that crumbles when hit with a hammer, but I would use one that breaks/splits.

Cheers.

Neill
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  #12  
Old 01-11-2009, 05:24 PM
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Default Re: Fire bricks versus 'Pressed Reds'

For anyone wanting 40% alumina firebricks and are willing to take a full pallet lot, we can offer @ $3 each. Melbourne based.
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  #13  
Old 01-16-2009, 03:56 AM
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Default Re: Fire bricks versus 'Pressed Reds'

how many are in a pallet load johnny?
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  #14  
Old 01-18-2009, 01:20 PM
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Default Re: Fire bricks versus 'Pressed Reds'

320 pcs sized 230x115x75.
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  #15  
Old 04-28-2015, 05:08 PM
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Default Re: Fire bricks versus 'Pressed Reds'

Quote:
Originally Posted by david s View Post
Neill,
I agree that the common reds are probably adequate for a home oven which is used fortnightly on average.That would equate to about 250 firings in about ten years. But I think it might be a different story if the oven were in a restaurant and being fired every night. I recall seeing many fireplaces in Victoria, which get a pretty good working over in winter, with crumbly red brick floors. I don't think that it is the temperature the bricks are fired to which is the crucial factor, but rather how refractory the materials the bricks are made of, that is the most important. Iron in Australian soils is predominant and gives the characteristic red colour, but also fluxes up the clay and makes it less refractory, hence the high price for the rarer fire clay.
Davids, How much do you buy your firebricks in Townsville?
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  #16  
Old 04-28-2015, 08:44 PM
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Default Re: Fire bricks versus 'Pressed Reds'

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Originally Posted by Volongo View Post
Davids, How much do you buy your firebricks in Townsville?
I don't buy firebricks anymore. I sold the last of them that I had about a year ago. I use. A castable refractory to make ovens, it is way easier than cutting bricks. Most commercial furnaces use castable now, which is gunned on rather than using firebricks. When the refractory is past it's serviceability it is broken up with sledgehammers and a new lot gunned on. Most firebricks in Australia are now imported and hence their high cost.
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Old 04-28-2015, 10:25 PM
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Default Re: Fire bricks versus 'Pressed Reds'

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Originally Posted by david s View Post
When the refractory is past it's serviceability it is broken up with sledgehammers and a new lot gunned on. Most firebricks in Australia are now imported and hence their high cost.
Ok. I was aware that you use castable refractory material for your oven, but just thought maybe you still use firebricks for the cooking floor. Using a sledgehammer to break the refractory material sounds like a good workout for me . Full body workout that!

The cheapest FB Iíve seen currently is $2.50 on special excluding delivery.

I have a question that you might be able to answer. What is the percentage make up of Metallic Oxides or specifically Iron Oxides in a typical clay pressed red here in Australia?

I understand that the chemical composition of one brick varies to next and from batch to batch, but I would love to see a technical data sheet detailing the average chemical composition of a clay pressed red?
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Old 04-28-2015, 11:28 PM
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Default Re: Fire bricks versus 'Pressed Reds'

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Originally Posted by Volongo View Post

I have a question that you might be able to answer. What is the percentage make up of Metallic Oxides or specifically Iron Oxides in a typical clay pressed red here in Australia?

I understand that the chemical composition of one brick varies to next and from batch to batch, but I would love to see a technical data sheet detailing the average chemical composition of a clay pressed red?
Yes the amount of iron contained in any clay body will vary considerably. It is particularly important for firebricks as iron acts as a flux and makes the silica turn to glass at lower temps. But this is not really a factor for the temperatures we fire to, it only comes in at temps over 1200 C. Most Australian clays are high in iron, this may explain why firebricks are usually imported and so expensive here. Suitability for a WFO is not so dependent on iron oxide content, it is more the thermal shock characteristics and this will vary greatly for common pressed reds.

To answer your question look here

http://www.traditionaloven.com/artic...re-clay-bricks

Last edited by david s; 04-28-2015 at 11:32 PM.
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Old 04-29-2015, 12:31 AM
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Default Re: Fire bricks versus 'Pressed Reds'

David, Thanks for the link, but I have read Rado's article on the firebricks, old red bricks as alternative etc.. The technical Data sheet is for a Fire Brick. I was curious maybe you have come across or know the technical data sheet for a red clay pressed brick.

I think you will agree with me that the content of a brick is very important as it determines its physical properties (strength). It is the strength properties of the material that determines its ability to withstand stress from expansion.

So yes, it is the thermal shock characteristics of the brick used that determines how long a WFO would last. By which Alumina has a higher strength (bonding) than silica or ferruginous clays. However, how significant the strength of alumina versus silica in relevance to WFO I am not entirely sure.
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  #20  
Old 04-30-2015, 03:10 PM
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Default Re: Fire bricks versus 'Pressed Reds'

Quote:
Originally Posted by Volongo View Post
David, Thanks for the link, but I have read Rado's article on the firebricks, old red bricks as alternative etc.. The technical Data sheet is for a Fire Brick. I was curious maybe you have come across or know the technical data sheet for a red clay pressed brick.

I think you will agree with me that the content of a brick is very important as it determines its physical properties (strength). It is the strength properties of the material that determines its ability to withstand stress from expansion.

So yes, it is the thermal shock characteristics of the brick used that determines how long a WFO would last. By which Alumina has a higher strength (bonding) than silica or ferruginous clays. However, how significant the strength of alumina versus silica in relevance to WFO I am not entirely sure.
Yes, i agree that the clay content is important, but no I don't agree with you that a fired clays strength determines its ability to withstand stress from expansion.
An example of this is a cob oven which not being fired at all has excellent thermal shock characteristics. Also the low fired pots made in South America, designed to be placed directly on a stove have good thermal shock characteristics, like wise raku clay pots which are removed directly from the kiln and dropped into water, have good thermal shock characteristics. Clays fired in the 1000 -1200 C (eathenware and stoneware) range don't have such good thermal shock characteristics, yet they are considerably stronger. Porcelain fired clays are good and are used for internal kiln bits and pieces like bung hole plugs and pyrometer probes which see big temperature changes, but at this temperature most clay bodies wil melt from the fluxes present. A brick manufacturer designs his bricks to be partly vitrified so they are partly waterproof yet can still breathe.Each batch of clay and each brick may have a different composition for house bricks because the clay is not highly processed. The manufacturer may not even be able to give you accurate details of his bricks composition. You may have bricks that will work ok or you may not. You'd have better chance with a creamy coloured brick than a red one.

Last edited by david s; 04-30-2015 at 03:17 PM.
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