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Extremely dark cone 6 clay bodies?


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I'm looking for some clay bodies that are DARK. I have an idea in mind, and I'd like to have a clay as dark as something like cassius basaltic clay. But I've seen that it's SO finicky, and a lot of people have their glazes crater on that clay.

I would like to achieve this kind of contrast between my clay and glaze:

468913574_ScreenShot2019-05-30at7_32_38PM.png.3c4a882f00e1180da87b2990f841243d.png

Sorry for the blur.

Does anyone know of a reliable, tested clay body that is dark chocolate or near black, and fires to cone 6?

*I know these clays can sometimes contain high levels of manganese. Does this render the piece non-food safe?

 

Edited by Tumbleweed Pottery
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13 minutes ago, liambesaw said:

Dark bodies have lots of iron disulphide in them, or lots of black stain in them, each have their issues.  My clay bodies fire a dark maroon, which is good, but also have issues with glazes that don't heal well as carbon and sulphur burn out.

Sounds like the best way to figure things out is to buy a 25lb bag, and fire a few test tiles with my intended glaze? Then if that works well, move to a small vessel?

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27 minutes ago, Tumbleweed Pottery said:

Sounds like the best way to figure things out is to buy a 25lb bag, and fire a few test tiles with my intended glaze? Then if that works well, move to a small vessel?

Absolutely!  And definitely slow bisque it.  I love the look of iron clay bodies though, so I try to adjust my glaze recipes to have a less viscous melt in hopes the holes will heal over.  Either that or just let the glaze have defects.

I'm gonna be trying out some porcelains tonight and see if I can throw/handle/like them as much as I do the dark bodies, we will see

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https://www.sio-2.com/us/language_changed/subfamily/93

This clay will do exactly what you want but is very expensive and problematic to throw well. *shrugs*

Maybe other's don't have a problem throwing it, but I for the life of me cannot get a pot higher than 12 inches with it, and I can throw all of the "difficult" porcelains just fine.

I have never had black ice bloat, and I have fired it all the way to cone 7, and I also have single fired it with no bisque. The clay is remarkable, and I don't know how they get the dark body, but it doesn't change the color of the glazes on top at all.

Here is a cup with the clay as a slip, which is how I use the clay as I prefer to use it as a slip on my work because of the texture I get using it. (plus its cheaper to use as a slip since I don't have to use nearly as much clay to get the look I am after.

The black area is the unglazed area with black ice. This is cone 6.

38789727_661956010837941_867310187056830

Edited by Joseph Fireborn
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Kentucky Mudworks Brown Bear is available in a 25# sample bag. I love this clay, along with all of their clays it's just really well made. Easy to form, low absorbency, most  glazes look great, particularly whites and other light colors.

Edit to add Laguna's WC-391/B3 is another alternative, you may be able to find a nearby supplier to save on shipping costs. It has more manganese (4% I believe) and so is slightly darker than the BB. It's also a nice clay, but be sure to have a good vent setup, my self-rigged updraft fan wasn't sufficient so I had to stop using it after 2 time because of the strong smell. Beautiful clay, though.

Edited by NancyAmores
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  • 3 weeks later...

Standard 710 is the same as 266 but with added grog - I fire it to a hot cone 6 without any bloating on thinly thrown mugs/bowls. It's a really nice clay to throw with! It does react strangely with some glazes so testing is key of course.

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11 hours ago, harleydp said:

Standard 710 is the same as 266 but with added grog - I fire it to a hot cone 6 without any bloating on thinly thrown mugs/bowls. It's a really nice clay to throw with! It does react strangely with some glazes so testing is key of course.

Grog will bump up the peak temp. Is it a coarse grog or fine? I could see 266 being really nice with fine grog. Also, is the grog visible in the fired clay?

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14 hours ago, neilestrick said:

Grog will bump up the peak temp. Is it a coarse grog or fine? I could see 266 being really nice with fine grog. Also, is the grog visible in the fired clay?

It is a fine grog and yes, it's visible in the fired clay. This is from Standard's website about 710: "Gives a reduction-like dark brown color in an electric kiln. Smooth and plastic. Contains manganese and a small amount of fine grog is added. It's good for all techniques. We recommend firing to cone 5."

Here is a bowl I did with 710 leaving the rim and foot unglazed (KY Mudworks Everglade glaze and Amaco Temmoku for the stripe)

IMG_3907.jpg

IMG_3912 2.jpg

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  • 6 months later...

Hello All,

I love that bowl you made, Harley DP.  Anyone have any experience finding a clear glaze that works on the 710 without pinholing and blistering? I ran a bunch of test tiles, C6, and none of my clear glazes came out well. Maybe I have to apply then paper thin to remove the blistering...

Please, any advice. 

On 6/20/2019 at 2:54 PM, harleydp said:

It is a fine grog and yes, it's visible in the fired clay. This is from Standard's website about 710: "Gives a reduction-like dark brown color in an electric kiln. Smooth and plastic. Contains manganese and a small amount of fine grog is added. It's good for all techniques. We recommend firing to cone 5."

Here is a bowl I did with 710 leaving the rim and foot unglazed (KY Mudworks Everglade glaze and Amaco Temmoku for the stripe)

IMG_3907.jpg

IMG_3912 2.jpg

 

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Hi Michael,

Clear that's working for me on red clay (Aardvark SRF) - clears the microbubbles - does fairly well on Aardvark Clay Cassius Basaltic, fwiw. Last glaze firing included a set of Basaltic test tiles and a small bowl. The other clear glazes either scabbed up or retained a froth of micro bubbles. The glaze is "Wollastonite Clear" 

https://community.ceramicartsdaily.org/topic/20620-does-anyone-recognize-the-source-of-this-glaze-recipe/

It didn't come out perfectly smoothed over on the bowl, which may be due to thickish walls; the test tile smoothed over nicely.

Solid cone 5, dropped 100F and held for fifty minutes, then free fall cool.

 

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29 minutes ago, neilestrick said:

@Michael D Try a slower bisque, especially the last 200 degrees. You may want to drop it down to 60F/hr to make sure you're getting everything burned out.

Thanks Neil! Will do. I also think that I was hasty in mixing my first test glazes, not sieving enough, and brushing them on too thickly,  The glazes all looked great on a white body, but on the dark 710 (which I love) they look horrible. (Which makes me think it has something to do with escaping gases from the body)

Michael

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Also, (sorry to hijack this thread).

My daughter made her first mugs (dark clay) and wanted to gift them to friends back at college. She is leaving soon and I don't want to rush it and ruin them. But I also need to have them finished by this weekend. If I fire a clear glaze on them and the glaze comes our with too many bubbles (making it opaque), is all lost? Can I fire it again and, say, soak longer, to clear the bubbles?

I'm planning on brushing on the glaze very thinly this time. And slow firing it to C6 with a soak at the peak, and short soak coming down. 

Michael 

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24 minutes ago, Michael D said:

She is leaving soon and I don't want to rush it and ruin them. But I also need to have them finished by this weekend. If I fire a clear glaze on them and the glaze comes our with too many bubbles (making it opaque), is all lost? Can I fire it again and, say, soak longer, to clear the bubbles?

I wouldn't count on it working. 

Are you adding brushing medium to these glaze recipes? It's difficult to brush on dipping glazes evenly without it.

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30 minutes ago, Michael D said:

Also, (sorry to hijack this thread).

My daughter made her first mugs (dark clay) and wanted to gift them to friends back at college. She is leaving soon and I don't want to rush it and ruin them. But I also need to have them finished by this weekend. If I fire a clear glaze on them and the glaze comes our with too many bubbles (making it opaque), is all lost? Can I fire it again and, say, soak longer, to clear the bubbles?

I'm planning on brushing on the glaze very thinly this time. And slow firing it to C6 with a soak at the peak, and short soak coming down. 

Michael 

Bubbles may or may not get better with refiring. Sometimes they get worse! A thin application should help in this case, though.

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"...Try a slower bisque..."

Aye! I've been following Nerd's bisque fire advice, particularly slowing down through 752F, 1063F, and 1500F

Detailed article:

https://community.ceramicartsdaily.org/topic/17903-critical-firing-temperatures/

Compilation of links:

https://community.ceramicartsdaily.org/topic/20132-slow-bisque-kiln-help/

Tony Hansen's article:

https://digitalfire.com/4sight/glossary/glossary_glaze_bubbles.html

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If there is a bit of iron in the clear it helps clear the bubbles. Liner glaze on red clay pot below, zero bubbles, nice and perfectly clear. I fiddled the recipe to fit this low COE clay but it started out as this one. I don't know if just adding some very fine iron to an existing clear would have the same effect. If you try this the amount of iron in the recipe I used is approx 3.5% (from the Alberta Slip). 

IMG_3096.jpeg.b51f037196ad0f9282f7e637478e702c.jpeg

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