Making clay 101

[Biglou13]

latest batch made and wedged in about a week,   drill mixer pillow case technique  ala marcia s.

my 50 pounds dry yielded 81 pounds wedged. prolly lost a few pounds to buckets and pillow cases.

ps.  maybe im a glutton for punishment  but i wedged 81 pounds of clay by hand,  cut and slam and traditional sprial ish wedging?

 

first mix got wodfired will try and pick up on friday. will post pics asap.

 

second batch i tweaked recipe.  ill post pics to compare when wood fired.

[Biglou13]

Saw a great clay body, Flashed red in wood fire, (frutani red ish)

 

Pried out recipe out of him.. 75 % cedar arts 50 mesh bonding. 25% gold art. After a little research I found out they are the same clay, only size is different!!! I can can see mr axe. Rolling his eyes.... And when Jedi' s roll their eyes padwan learner spat attention.

Ok the clay performed spectacularly in wood fire. Also was told it performs well at cone 6 ox electric and loved almost all glazes. It's cheap, performs well across broad spectrum of temps and glazes.....easy recipe, cheap, Yohen!, there is data along with test tile on digital fire.

 

Ok sounds to good to be true......so I'm suspect, No disrespect to teacher who passed it on.

 

Any one with any experience with this?

Comments?

 

( thinking out loud thinking of adding small ish percentage epk/and or helmer along with appropriate amount of nepsy, Custer, But will test as is )

[Guest JBaymore]

If that is the WHOLE recipe above... it will tend to develop cristoolite in extended wood firings..... not enough glassy phase to tie up the inherent free silica and the silica ejection from the clay crystals when chemical water is driven off.  Don;t doubt the color rendition though.

 

Remember my comments (elsewhere) about some of the best LOOKING bodies being "bad" clay bodies.

 

best,

 

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

[Biglou13]

If that is the WHOLE recipe above... it will tend to develop cristoolite in extended wood firings..... not enough glassy phase to tie up the inherent free silica and the silica ejection from the clay crystals when chemical water is driven off.  Don;t doubt the color rendition though.

 

Remember my comments (elsewhere) about some of the best LOOKING bodies being "bad" clay bodies.

 

best,

 

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

Sensei (yoda)...... I forget nothing you say. Hopefully I won't have to pour boiling water on this body. Often beauty comes from radical thought, walking on the edge and pushing the envelope, safe is often just that, I like the idea that this body is somewhat outside of the box..... The bizen (silty) body will have to wait. ( although it has similar red flashy hi iro). My next tests will be with gold art, cedar art

[Biglou13]

Made clay today very small batch under 5 # dry mix.

$6 drill from pawn shop

$7 mixing tool

$12 scale

$0 5qt bucket I had

$0 Old pillow case part 1of 2 hight tech clay drying system

$1. High tech root maker pot aka clay drying system

$0. Rain water collected

 

Making your own clay......... Priceless

 

The mix in picture will hopefully be a very flashy in woodfire.

 

I use three 5 gal buckets for 50# batch.

[Biglou13]

If that is the WHOLE recipe above... it will tend to develop cristoolite in extended wood firings..... not enough glassy phase to tie up the inherent free silica and the silica ejection from the clay crystals when chemical water is driven off. .........

 

best,

 

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

Found this on net...

 

"........If feldspar is present in the body then any available molecular silica is taken up in the formation of silicates, and thus cristobalite does not form. If it does then it too is taken into solution. A good strategy in formulating a body is to use enough spar or naturally fluxed clays to be sure that any potential cristobalite is drawn into body glass (check with dilatometer test) and then re-establish fit with fine quartz. In this way quartz is compressing the glaze at 573C rather than cristobalite at 220C. A typical cone 10 porcelain with 25-30% feldspar will show no evidence of cristobalite on its expansion curve (as measured in a dilatometer). Conversely, high iron often non-vitreous stoneware bodies can generate high cristobalite levels........" (Hansen, T. (2008). Cristabolite. Retrieved from http://digitalfire.com/4sight/glossary/glossary_cristobalite.html)

 

After reading your post John, and more time on net, and my notes. I went off a tangent from the 70/30. Here is my attempt at a flashy body for woodfire, yet stable at lower temps. And pictured in a previous post. (Also inspired by ingredients on hand)

 

Gold art 55

Saggar. 15

Helmer. 11

Lizella. 5

Feldspar. 9

Nepsy. 5

[neilestrick]

Also was told it performs well at cone 6 ox electric and loved almost all glazes. It's cheap, performs well across broad spectrum of temps and glazes....

 

If it can handle several days in a wood firing, it will be way too loose at cone 6.

[jrgpots]

I have followed a few threads about water in the clay making.....some say rain water only. Others say distilled is best. Could you use tap water that is run through a filter removing chlorine, some Na and K ions? What type of effects would using reverse osmosis (RO) filtered water create, since the RO system removes all ions? Does it make much of a difference?

 

Jed

[Biglou13]

I can't say from a ceramics chemistry point. But all those impurities in water are very very very minute. Municipal water systems are relatively clean, I doubt that tap vs ro vs distilled vs rain would make that big a difference in clay body. I'm not doubting there is some effect, or affect on the clay. But I think there. Are bigger fish to fry, when it comes to clay bodies.

 

It's h2o also what is locally sourced. In pre modern society they used what they had. Sure I'm using manufactured clays, much of it local, but I have to draw the line worrying about water. Many around primary water sources are wells. I plan on using well water for my next clay. Actually there is a spring near the studio, sulfur smell in water. John b. Spoke about local clays in japan. I think it's these subtleties that make the beauty in a clay body. Kind like bread or bagels in newyork city. People say it's the water. On anagama-west website there a recipe where they tried to replicate shigariki clay at a chemical level, while the clay was functional, it was a failure in replicating.

I m hoping my local water adds flavor to my clay

[Biglou13]

inspired by ingredients on hand looking for a flashy woodfired clay body.....

 

Gold art 55

Saggar. 15

Helmer. 11

Lizella. 5

Feldspar. 9

Nepsy. 5

 

Any opinions to from any of the gurus of clay...... Or anyone?

[Biglou13]

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.

[Biglou13]

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.

[Guest JBaymore]

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

[Biglou13]

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?

[Guest JBaymore]

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"  .  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

[jrgpots]

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

[Biglou13]

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)

[Biglou13]

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.

[Biglou13]

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?

[Guest JBaymore]

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.

[Biglou13]

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?

[Marcia Selsor]

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

[neilestrick]

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?

[Min]

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)

[Biglou13]

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.