Jump to content


Photo

Making clay 101


  • Please log in to reply
103 replies to this topic

#61 Biglou13

Biglou13

    Advanced beginner pottery, Advanced in other art

  • Members
  • PipPipPip
  • 874 posts
  • LocationNorth Florida

Posted 22 October 2013 - 08:01 PM

Here is preliminary results from wood fire for with modified d12 clay body see earlier posts.
I'll get better pictures in am. Just drove over six hours (and worth it)

It definitely carbon traps, and took a good coat of ash glaze I'm surprised the piece is so glassy, and closed body. a lot of ash glaze, wad is stuck, I'll try operating later.... Look closely in center. Some pooled green ash glaze. I didn't expect this, the kiln gods were kind to me.

I'm very happy with results. The results well exceeded my expectations. This is my first wood firing. I'm officially addicted.

Attached Files


Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#62 Biglou13

Biglou13

    Advanced beginner pottery, Advanced in other art

  • Members
  • PipPipPip
  • 874 posts
  • LocationNorth Florida

Posted 22 November 2013 - 10:29 PM

Ok I want to make a cone 6 ox Clay a dark body. Standard 266 ish. So I tried to get some blackbird or Barnard to go into the mix. Supplier didn't have it. He suggested Alberta slip which is dark, but I have seen little to no info about it as a clay body component.

So far planning (loosely).....(It's what I have on hand)

25 gold
23 #4
15 Hawthorne
13 lizella
10 silica
10 custer
5 nepsy

3 manganese
1 cobalt
5 albany

Any ideas??? Comments ,suggestions?

Stay tuned results on 2 previous clays coming soon as I can see daylight.
Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#63 JBaymore

JBaymore

    Moderator

  • Moderators
  • 2,796 posts
  • LocationWilton, NH USA

Posted 23 November 2013 - 11:33 AM

Biglou,

 

When you add manganese bearing compounds into you clay body, which is something that you use in bulk all around the studio, you are adding mangenese compounds into the respirable dust that is always an issue from dry claybody stuff in the studio envoronment.  Just be aware of this fact in the decision making process.

 

Granular manganese for 'speckling" (as long as the "fines" are taken out) is one thing (not respirable).  Powdered manganese or the manganese from stuff like Blackbird/Barnard is another.

 

best,

 

.....................john


John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#64 Biglou13

Biglou13

    Advanced beginner pottery, Advanced in other art

  • Members
  • PipPipPip
  • 874 posts
  • LocationNorth Florida

Posted 23 November 2013 - 01:08 PM

so you sayin that dark bodies eg 266,  blackbird, barnard all contain dangers with manganese exposure

 

is the albany/ alberta slip a safer  "dark"  agent

 

will the lizella, cobalt. rio make a darker body.

 

are there safer alternatives to making a dark clay body.

 

i suppose ill test clay without manganese.

 

 

i am testing a manganese and white slip    under other glazes (clear, shino ish) that have a runny/drippy manganese look .   pretty minimal exposure.   is this something i should worry about.  i never see other than in container and under a glaze and washing a brush.  and after its fired i understand its safe?


Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#65 JBaymore

JBaymore

    Moderator

  • Moderators
  • 2,796 posts
  • LocationWilton, NH USA

Posted 23 November 2013 - 01:41 PM

so you sayin that dark bodies eg 266,  blackbird, barnard all contain dangers with manganese exposure

 

Since the suppliers generally will not share what is actually in their bodies, it is impossible to say for sure.  But some appear (if you know "what causes what" in ceramics) to contain such materials.  If so "yes".

 

Note (as I mentioned elsewhere in anotehr recent thread) those ASTM "non-toxic labels on most clay boxes (and the info in many MSDSs) apply only to the clay (or glaze) being certified in the WET state.  Hard to inhale 25 pounds of plastic clay ;) .

 

Evaluating all of the H+S stuff depends on your overall potential exposures, and that "look see" has to include the exposures you get from all of the other sources in your life. I spend a bunch of time on this stuff in my ceramic chemistry courses.  If you are a hobbiest, and use a total of 100 pounds of wet clay a year......  your situation is very different from a pro that is using 10,000 pounds of clay a year.  A peson doing "colored clay" (neriage/nerikomi) kinds of work is using clays that contain lots of colorants.... but they are usually working in a very slow process.... and thereby even if full time........ are not processing the huge amounts of clay per day/week/month that a thrower might.  If you are a ceramist that is not exposed to silica dust from any other sources, that is different from if you are ALSO an off-road motorcyclist that is breathing dust all the time.  And so on. 

 

To shift toward the gray / black tones in bodies, the usual selection is a manganese bearing compound.  High iron will only get you so dark ..... and it tends toward the reddish/brownish tranges of color.  Look at earthenwares... for example... high iron bodies.

 

Cobalt compounds are not as innocous as most potters seem to think they are.  I don't know why,...... maybe because they make a "pretty blue" :P .  Check out the H+S info and stuff like MSDSs and the PELs/TLVs for cobalt compounds.

 

Awareness is the improtant part here, not "panic" :) .  If you know about what you are handling, you can take appropriate precautions and make appropriate informed decisions.

 

best,

 

...........................john


John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#66 jrgpots

jrgpots

    The hands can express the soul

  • Members
  • PipPipPip
  • 450 posts
  • LocationHurricane, Utah

Posted 24 November 2013 - 10:54 PM

so you sayin that dark bodies eg 266,  blackbird, barnard all contain dangers with manganese exposure
 
is the albany/ alberta slip a safer  "dark"  agent
 
will the lizella, cobalt. rio make a darker body.
 
are there safer alternatives to making a dark clay body.
 
i suppose ill test clay without manganese.
 
 
i am testing a manganese and white slip    under other glazes (clear, shino ish) that have a runny/drippy manganese look .   pretty minimal exposure.   is this something i should worry about.  i never see other than in container and under a glaze and washing a brush.  and after its fired i understand its safe?


I don't know if this would help,,,,I have some betonite that fires to dark brown, melts below cone 5, and is free for the taking. Very plastic!

Jed

#67 Biglou13

Biglou13

    Advanced beginner pottery, Advanced in other art

  • Members
  • PipPipPip
  • 874 posts
  • LocationNorth Florida

Posted 25 November 2013 - 11:00 AM

Modified, Modified 12 d clay....
Super glassy mother of pearl like metallic red flashing, carbon trapping.
Low res images do little justice. I have never seen this much "bling" in a woodfired piece.
Yeah this body is a keeper. (Hope I can get similar results with next batch)
More pics in gallery

Big thanks to
Sensei John B, atomic axe, off center, Marcia, mark, old lady, and to any one else who helped me. I've learned volumes about clay and pottery in getting this to work.

(And to the naysayers this pot thumbs it nose at you)

Attached Files


Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#68 Biglou13

Biglou13

    Advanced beginner pottery, Advanced in other art

  • Members
  • PipPipPip
  • 874 posts
  • LocationNorth Florida

Posted 25 November 2013 - 11:22 AM

Results of this clay

Gold art 55
Saggar. 15
Helmer. 11
Lizella. 5
Feldspar. 9
Nepsy. 5

My attempt at flashy woodfired body.
Pleased it worked, pretty flashy but I'm going to tweak a few percentages here and there for next batch.
Only got one piece back so I'm holding back on final opinion until I see more and from from different parts of kiln.
My Opinion over all happy with it. My first body that came from my head (not based on others recipe) got some good flash, it took to the ash well. And held up to cone 13 3 day firing. Interested if straw wrapping would produce bizen like flashing. Body in General was too dark I was thinking a lighter overall colored body and will tweak it a bit.

Attached Files


Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#69 Biglou13

Biglou13

    Advanced beginner pottery, Advanced in other art

  • Members
  • PipPipPip
  • 874 posts
  • LocationNorth Florida

Posted 27 December 2013 - 08:09 PM

I'm was going to make this again , a larger batch

Gold art 55
Saggar. 15
Helmer. 11
Lizella. 5
Feldspar. 9
Nepsy. 5

I realized I'm out of saggar xx clay. I do have hawthorn 40 Any opinions on subbing?
Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#70 JBaymore

JBaymore

    Moderator

  • Moderators
  • 2,796 posts
  • LocationWilton, NH USA

Posted 28 December 2013 - 12:28 PM

Interested if straw wrapping would produce bizen like flashing. Body in General was too dark I was thinking a lighter overall colored body and will tweak it a bit.

 

The particular wrapping is RICE straw... not just straw.  I've done a lot of this and spent much time trying to find some "straw" that duplicates the result.... with little luck.  I can get some hiduski, but not as nice as from rice straw. A straw that grows along the river bank near the noborigama here works the best of anything I have found yet.  I have no idea what the genus/species is.

 

I now use rice straw most of the time.  It is a bear to obtain here in NH.

 

"Salt hay" from the feed and grain store works a bit ... but not like rice straw.

 

My firends in Japan do NOT soak it in any brine solution.  I've tried brine... and you have to be VERY careful the solution saturation.  Less is more. 

 

Note that the basic technique is to wrap the piece and then place it inside (fully or partially) a surrounding container to protect it from the kiln atmosphere.  This keeps the burning rice straw in localized contact with the form, and keeps the ashes in place instead of blowing/falling away.

 

best,

 

..........................john

 

PS: note form that plate.... often for plates, stack them upside down on wads... the bottom side often has the better results.


John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#71 Biglou13

Biglou13

    Advanced beginner pottery, Advanced in other art

  • Members
  • PipPipPip
  • 874 posts
  • LocationNorth Florida

Posted 18 February 2014 - 09:04 PM

Some of the clay bodies I make have nep Sy as flux.
I've read that. Nep Sy can cause deflocculation in a moist clay body. I'm not talking about slip clay.
The description of a deflocculated clay body was a bit vague. There was some mention of thixotropy.
From I got from my limited research is caused because nepsy creates a charged particle. And as it drys it forms a "crust" leaving the inside gooey. Which causes handling and cracking issues.
The clay bodies contain approx 25% nepsy.
The clay is a bit delicate in moist, drying stage. I dry this clay body painfully slow. And will still get occasional saw crack, or general crack.
And unless groged it's pretty difficult to get clay to leather hard state to slab build.
Unfortunately many mid fire clay body recipes call for nepsy as flux since it a "lower temp" flux. That helps "glass up" in mid range.

Can someone please explain deflocculation of a most clay body please?
Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#72 Marcia Selsor

Marcia Selsor

    Professor Emerita, Montana State University-Billings

  • Members
  • PipPipPip
  • 3,739 posts
  • Locationwhere Texas, Matamoros, Rio Grande and Gulf of Mexico come together.

Posted 18 February 2014 - 09:47 PM

I would recommend letting your dry mix slake in the wet mix at least overnight before you pour it into pillow cases. The lumps all be less pronounced.
Marcia

#73 neilestrick

neilestrick

    Neil Estrick

  • Members
  • PipPipPip
  • 2,429 posts
  • LocationGrayslake, IL

Posted 18 February 2014 - 10:18 PM

Some of the clay bodies I make have nep Sy as flux.
I've read that. Nep Sy can cause deflocculation in a moist clay body. I'm not talking about slip clay.
The description of a deflocculated clay body was a bit vague. There was some mention of thixotropy.
From I got from my limited research is caused because nepsy creates a charged particle. And as it drys it forms a "crust" leaving the inside gooey. Which causes handling and cracking issues.
The clay bodies contain approx 25% nepsy.
The clay is a bit delicate in moist, drying stage. I dry this clay body painfully slow. And will still get occasional saw crack, or general crack.
And unless groged it's pretty difficult to get clay to leather hard state to slab build.
Unfortunately many mid fire clay body recipes call for nepsy as flux since it a "lower temp" flux. That helps "glass up" in mid range.

Can someone please explain deflocculation of a most clay body please?

 

Neph Sye, which is a soda spar, has a small amount of soluble soda in it, so it can deflocculate the body somewhat. I have used a lot of clay bodies that have Neph Sye in them, including porcelains, and have never had a problem with it. It looks like more of an issue on paper than in reality in my experience. If a body has 25% in it, them I imagine it's also high in silica, and low in clay, like a porcelain? I would expect that is the issue more than the deflocculation. Care to post a recipe?


Neil Estrick
Kiln Repair Tech
L&L Distributor
Owner, Neil Estrick Gallery, LLC
www.neilestrickgallery.com

neil@neilestrickgallery.com

#74 Min

Min

    Advanced Member

  • Members
  • PipPipPip
  • 395 posts
  • LocationCanada

Posted 18 February 2014 - 11:18 PM

Some of the clay bodies I make have nep Sy as flux.
I've read that. Nep Sy can cause deflocculation in a moist clay body. I'm not talking about slip clay.
The description of a deflocculated clay body was a bit vague. There was some mention of thixotropy.
From I got from my limited research is caused because nepsy creates a charged particle. And as it drys it forms a "crust" leaving the inside gooey. Which causes handling and cracking issues.
The clay bodies contain approx 25% nepsy.
The clay is a bit delicate in moist, drying stage. I dry this clay body painfully slow. And will still get occasional saw crack, or general crack.
And unless groged it's pretty difficult to get clay to leather hard state to slab build.
Unfortunately many mid fire clay body recipes call for nepsy as flux since it a "lower temp" flux. That helps "glass up" in mid range.

Can someone please explain deflocculation of a most clay body please?

 

Sounds like you are describing some of the “joys” of using porcelain. Jeff Campana’s porcelain, uses F-4 (Minspar now I’m guessing) and a little Ferro 3110 for the fluxes instead of nepsy. Julia Galloway’s porcelain uses 23% nepsy, after trying both bodies I can’t say there is much noticeable difference between them. (let me know if you want the recipes)



#75 Biglou13

Biglou13

    Advanced beginner pottery, Advanced in other art

  • Members
  • PipPipPip
  • 874 posts
  • LocationNorth Florida

Posted 19 February 2014 - 08:29 PM

neil:

http://www.anagama-w...clay_bodies.php

Slightly Modified Lehman D12
EPK 36.80
Nepheline Syenite 24.50
OM4 Ball Clay14.30
Silica19.10
Bentonite5.10
Redart2.50
Sum102.30
This slightly Modified Lehman 12-D is derived from the recipie contained in Dick Lehman's article A New Approach To Long-Fire Results

 
i lowered the bentonite with slurry method clay was too buttery.
 
min yes please chare recipes either here or pm.

Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#76 Min

Min

    Advanced Member

  • Members
  • PipPipPip
  • 395 posts
  • LocationCanada

Posted 20 February 2014 - 12:34 AM

min yes please chare recipes either here or pm.

 

 

Campana Midrange Porcelain Cone 5-8

 25 Grolleg

10 C&C Ball Clay

 10 Tile #6 Kaolin

 35 Minspar

 20 Silica 325 Mesh

 2.5 Bentonite L-10 White

 

I messed around with this and subbed in some 3110 for part of the flux, my version of his clay is:

22  Grolleg

9  C&C Ball Clay

14  Tile 6

32  Minspar

20  Silica 200 mesh

5  Ferro 3110 

3 Bentonite, white

 

Galloway Porcelain Cone 6

35  EPK

15  Tile 6

5  Sagger XX Ball Clay

23  Nepsy

22  Silica

3  Bentonite, white

 

The Campana ones are nice and white, throw pretty well but are expensive to make up because of the grolleg. I found the Galloway one throws better, handles etc have less cracking but it’s cream not white. When I went to school I was taught that porcelains don’t contain ball clay, so if these can be called porcelains is open to interpretation. I know most ^10 potters will say there is no such thing as a ^6 porcelain anyway  ^_^

 

Your Slightly Modified Lehman D12 looks quite close to the Galloway one. 



#77 Biglou13

Biglou13

    Advanced beginner pottery, Advanced in other art

  • Members
  • PipPipPip
  • 874 posts
  • LocationNorth Florida

Posted 20 February 2014 - 07:30 AM

I like the Galloway recipe

I live near the epk mine and is inexpensive. ( relatively). However the 12D is technically a cone 10 and up clay for woodfire. It super flashy in wood fire, broken pieces reveal a "bluish" body.

But yes I also fire some of the pieces electric.

I'm runniing formal tests now, Shrinkage, and vitrification/absorption

But from the recipes and from what I've read. I've seen similar bodies go from 3% (Ish) @cone 6 to .5% at cone 10.. The vitrification rate across temperature ranges is much narrower than other types of clay.

Non scientific testing indicates the the clay works at cone 6. I drink out of one every day.

I also made (recently) a 12d* that ads 36.8 ap green fire clay to 12d I replaced ap green with Hawthorne bond and it improved the clays working characteristics. Throwing feel drying, it's not as finicky.

I like the Galloway recipe with addition of saggar xx. Probably improves throwing charteristics. And saggar xx is proven performer in woodfire. I'll bet that Galloway recipe would hold up and be beautiful in wood fire.
Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#78 neilestrick

neilestrick

    Neil Estrick

  • Members
  • PipPipPip
  • 2,429 posts
  • LocationGrayslake, IL

Posted 20 February 2014 - 09:29 AM

 

neil:

http://www.anagama-w...clay_bodies.php

Slightly Modified Lehman D12
EPK 36.80
Nepheline Syenite 24.50
OM4 Ball Clay14.30
Silica19.10
Bentonite5.10
Redart2.50
Sum102.30
This slightly Modified Lehman 12-D is derived from the recipie contained in Dick Lehman's article A New Approach To Long-Fire Results

 
i lowered the bentonite with slurry method clay was too buttery.
 
min yes please chare recipes either here or pm.

 

 

What you've got there is what I would call a domestic porcelain with some Redart added for color. And like I suspected, it's quite low in clay. Plus the clays that are in it are very fine grained, especially the ball clay and bentonite, both of which have high drying shrinkage rates. So I'm not surprised that it's finicky and prone to cracking. I'm also not sure why it needs that much Bentonite when it's got 14% ball clay in it. I would start reducing the Bentonite and see if the cracking issues improve. As you mentioned, adding fire clay will make it much more workable, as it improves the particle size distribution. I would replace the ball clay with fireclay.

 

Another really nice cone 10 body you may want to try is and equal parts body, 20% each fireclay, kaolin, ball clay, feldspar and flint. You could add a little Redart for color.


Neil Estrick
Kiln Repair Tech
L&L Distributor
Owner, Neil Estrick Gallery, LLC
www.neilestrickgallery.com

neil@neilestrickgallery.com

#79 Biglou13

Biglou13

    Advanced beginner pottery, Advanced in other art

  • Members
  • PipPipPip
  • 874 posts
  • LocationNorth Florida

Posted 20 February 2014 - 10:58 PM

I would recommend letting your dry mix slake in the wet mix at least overnight before you pour it into pillow cases. The lumps all be less pronounced.Marcia


I have two buckets of recovery/ new clay mix. Slaking as we speak. Thanks
Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#80 Biglou13

Biglou13

    Advanced beginner pottery, Advanced in other art

  • Members
  • PipPipPip
  • 874 posts
  • LocationNorth Florida

Posted 20 February 2014 - 11:11 PM

Neil are you suggesting replacing all or part of ball clay.

"A popular buff firing plastic Missouri fireclay of fine particle size. It fires a light color with approximately 10% shrinkage at cone 10. Ground to 35"-- digital fire.com

I think I have Hawthorne 40 mesh. Which would be even smaller particle size. Nonetheless it feels better. Yet to se how it performs under wood fire. But I trust the source dick lehman.

I do have some sagger xx. Not sure on particle size. S Would this work as well and it's known to flash well.

Never considere particle size in formulating clays? Is it better to include wide range of particle sizes?

What is your concern with silca in body?

When you say flint I assume that is silica?
Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users