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Clay Composition - Kaolin


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Hi!

 

I've been researching on what the best clay composition I can use for floor tiles, looking at 1-3% water absorption after firing. A supplier offered me this clay composition (see photo). It's Kaolin clay, with 87-88% whiteness. Our idea is that we wouldn't have to go through applying engobe on top of the tile to make the surface white, since the clay is pretty white already we can print on it directly after drying (is this right?)

 

We're starting a bespoke tile company, and we are quite new at this so we would definitely have to hire experts to help plan everything. I was told this is ready to use clay, just use the hydraulic press with it and it's good to go. 

 

Any clay nerds around who can help? Thank you so much in advance! We have absolutely no knowledge of the proper composition for this!

 

 

 

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post-86704-0-44616800-1502270975_thumb.jpeg

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The specification you show are typical for most kaolin. The exception however, is very low titanium; which will increase whiteness and translucency if properly fluxed. The iron level is also low enough that it will not effect fired whiteness.

The more expedient questions are: what is the SAS, and or particle size of this clay.

What is the magnesium level? Not shown in specs. Higher MGO levels can cause grey casting of the finish piece.

What is the carbon content / sulfate level? 15% LOI concerns me, on the high side for kaolin. 15% LOI would have a direct effect on fired shrinkage. If the plasticity value is based in Atterberg Limits, then someone screwed up the test. Kaolin only comes in two plasticity ranges, not so plastic, and not plastic at all.

 

If all you are planning to do is tile, then particle size, MOR ratings, LOi, and metal oxide levels will be important factors. You will have to keep shrink rates down around 10%, if you get into any type of design work. What cone temp are you firing to? You will have to set flux molarity for that cone. 1-3% absorption for fully vitrified porcelain is high, under 1% is the goal.

 

Nice picture of raw freshly mined clay, sitting in a drying bin waiting to be processed. As catchy as it is: how do they process it? Air- floated, slurries, rotary grinders, magnet milling, or centrifugal particle separation? For tile, a wide spread of particle size would be nice.

 

Nerd

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As is, it's not ready to use. Raw kaolin needs to be incorporated into a body or glaze formula to be used for press moulds or throwing or whatever. Silica and a flux are generally additions you would want to make.--to make porcelain. Do you know the name of the kaolin? That would help immensely.

 

To be honest. I woukd say clay is the last piece of the puzzle and, quite frankly, the cheapest consumable you'll be regularly buying. That's not to say cheap, but cheap enough that you can buy according to performance need, not savings. I would get your all your other ducks in a row before taking the leap and buying clay. That way you'll be able to educate yourselfabout what clay you need to make the product you want. You may find this clay is perfect, or not. You may never even want to mix your own body and just hire that out. In which case, you don't need raw kaolin. But figure out your needs first, talk to those professionals, and then revisit the clay question.

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Thank you for all the replies, this is indeed very helpful! 

 

The specification you show are typical for most kaolin. The exception however, is very low titanium; which will increase whiteness and translucency if properly fluxed. The iron level is also low enough that it will not effect fired whiteness.
The more expedient questions are: what is the SAS, and or particle size of this clay.
What is the magnesium level? Not shown in specs. Higher MGO levels can cause grey casting of the finish piece.
What is the carbon content / sulfate level? 15% LOI concerns me, on the high side for kaolin. 15% LOI would have a direct effect on fired shrinkage. If the plasticity value is based in Atterberg Limits, then someone screwed up the test. Kaolin only comes in two plasticity ranges, not so plastic, and not plastic at all.

If all you are planning to do is tile, then particle size, MOR ratings, LOi, and metal oxide levels will be important factors. You will have to keep shrink rates down around 10%, if you get into any type of design work. What cone temp are you firing to? You will have to set flux molarity for that cone. 1-3% absorption for fully vitrified porcelain is high, under 1% is the goal.

Nice picture of raw freshly mined clay, sitting in a drying bin waiting to be processed. As catchy as it is: how do they process it? Air- floated, slurries, rotary grinders, magnet milling, or centrifugal particle separation? For tile, a wide spread of particle size would be nice.

Nerd

Thank you for this! I guess this is not the right one for us. The company could actually make a specific clay for us (so they say) given the proper information. We originally aimed for 1-3% absorption to keep costs down as I was told that fully vitrified tiles are more expensive to produce. Would this be because of higher firing temps?

 

Is there any place I could also get a clay recipe that I could give to manufacturers to produce for us?

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As is, it's not ready to use. Raw kaolin needs to be incorporated into a body or glaze formula to be used for press moulds or throwing or whatever. Silica and a flux are generally additions you would want to make.--to make porcelain. Do you know the name of the kaolin? That would help immensely.

 

To be honest. I woukd say clay is the last piece of the puzzle and, quite frankly, the cheapest consumable you'll be regularly buying. That's not to say cheap, but cheap enough that you can buy according to performance need, not savings. I would get your all your other ducks in a row before taking the leap and buying clay. That way you'll be able to educate yourselfabout what clay you need to make the product you want. You may find this clay is perfect, or not. You may never even want to mix your own body and just hire that out. In which case, you don't need raw kaolin. But figure out your needs first, talk to those professionals, and then revisit the clay question.

Hi Tyler, thank you for this. we are actually looking for professionals for hire in this forum. As it is now we are trying to figure out the capital needed for a small sized factory. As for mixing our own body, no idea how to do that, how hard (or easy it is?) but our first choice is probably to hire that out. I just need a clay recipe to show the manufacturers. Would you know where I can get one based on what we need?

 

Your input is well appreciated. Thank you

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I would recommend contacting the ceramics dept at Alfred university (specifically the Inamori school of ceramic engineering) to find someone to hire. With all due respect to everyone on this forum (I count myself among this group), we're just not experienced in what you're trying to do. You want a different kind of clay body from what we use, even if we go for the same things like final porosity and firing temp. There's a whole separate art to making tiles and organizing a factory to be profitable and efficient.

 

The reason fully vitrified ware is more expensive to produce is because of an increased failure rate. More chance pf warping slumping etc. As for clay body recipes, they're easy enough to come by (and formulate) once you know what you want. Easier to engineer a body around your setup than to setup around a body. And since hydraulic press moulds don't need plasticity, the sky is the limit.

 

Get your setup figured out, and by then you'll be educated enough to know what you want and how to get it. I think a mod here has conmections at Alfred, perhaps he would be so good as to hook you up via PM.

 

Cheers

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"Thank you for this! I guess this is not the right one for us. The company could actually make a specific clay for us (so they say) given the proper information. We originally aimed for 1-3% absorption to keep costs down as I was told that fully vitrified tiles are more expensive to produce. Would this be because of higher firing temps?"

 

Tile bodies can be fully vitrified at lower temps, talc bodies are often used in commercial manufacturing. However, they also use 100 ton presses, and only 4-5% moisture content so they can be fired immediately.

 

I assume you are looking at porcelain for specific reasons. " functional" tile use means installation in high moisture ares ( showers for instance), which means absorption has to be under 1% to prevent mold and grout failure from long term exposure.

A basic cone 6 porcelain body is 50% kaolin, 20% silica! and 30% feldspar. In your case, a very small amount of plasticizer such as bentonite (2-3%). This simple recipe will produce a tile body with absorption around 1%. The trick then becomes particle size, to ensure mechanical strength, and enough plasticizer to ensure the porcelain has no memory. Basically a "short" clay, as it is referred to in the business. Too much plasticizer translates into high memory, which translates into a lot of warped tiles.

 

There are many ways to formulate a body to kill plasticity, increase density, and still be cost effective.

 

Nerd

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"Thank you for this! I guess this is not the right one for us. The company could actually make a specific clay for us (so they say) given the proper information. We originally aimed for 1-3% absorption to keep costs down as I was told that fully vitrified tiles are more expensive to produce. Would this be because of higher firing temps?"

 

Tile bodies can be fully vitrified at lower temps, talc bodies are often used in commercial manufacturing. However, they also use 100 ton presses, and only 4-5% moisture content so they can be fired immediately.

 

I assume you are looking at porcelain for specific reasons. " functional" tile use means installation in high moisture ares ( showers for instance), which means absorption has to be under 1% to prevent mold and grout failure from long term exposure.

A basic cone 6 porcelain body is 50% kaolin, 20% silica! and 30% feldspar. In your case, a very small amount of plasticizer such as bentonite (2-3%). This simple recipe will produce a tile body with absorption around 1%. The trick then becomes particle size, to ensure mechanical strength, and enough plasticizer to ensure the porcelain has no memory. Basically a "short" clay, as it is referred to in the business. Too much plasticizer translates into high memory, which translates into a lot of warped tiles.

 

There are many ways to formulate a body to kill plasticity, increase density, and still be cost effective.

 

Nerd

 

THANK YOU! I'll reply to this thread once I have more information. Can't thank you enough for your feedback. 

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