Feldspar Chunks

[Biglou13]

There were posts earlier regarding feldspar chunks in wood fired pieces. A friend has found some feldspar mica mix. Is that the stuff. Is there a spec size that feldspar chunks come in. Friend of mine is at pacer Custer feldspar. What should I ask for?

[jrgpots]

Let us know what he says. I have 200 acres of granite rocks and decomposing granite dust. Most of the dust is feldspar and mica. I have a 5 gal bucket of this dust that has been sieved to 40 mesh sitting in my studio (ok, my garage). I'd love to follow what you plan on doing with your feldspar and mica.

[Biglou13]

Inclusions in clay bodies, primarily for, wood fired pottery

 

Granite inclusions Similar to shigariki style clay.

 

http://ceramicartsdaily.org/community/gallery/image/542-shigaraki-style-yakishime-vase-form-john-baymore-seacoast-master-artists-invitational-2010/

 

J baymore's work

[jrgpots]

Now that is cool. I was going to make a granite and ash glaze. I think I will add some larger pieces to the glaze. I am already adding scoria dust (lava dust) to laguna 50/50 clay for a great "cookies and cream clay." I will try the same thing with the granite.

 

You may want to try sieving with 20 mesh followed by 40 mesh and use what does not pass through the 40 mesh in your clay body. It should be about the right size to create the affect in your pic..... Although I bet you already know that. Please post your results and i will too.

[bciskepottery]

Judy Duff is a wood fire potter who also uses feldspar chunks.  http://www.judithduff.com/  Also, Akira Satake adds them to his work that is wood fired.  http://akirasatake.com/

 

You can add various sizes, the longer the firing, the better the melt if the chunk is large, e.g., pebble size (I think both of the above do 5 to 7 day firings).  If your firing is shorter, then a smaller size piece is more likely the right size for melting. 

[timbo_heff]

Sheffield has the custer feldspar chips but the are kind of sharp. I heard that pacer/custer has a more pebble shapped version which they were supposed to send: ask your friend at pacer if they have those because the chips will be really painful if they are included in a throwing body!

[Biglou13]

I called pacer/custer feldspar direct they were supposed to call me back today but that never happened.... Yet.

[Guest JBaymore]

Hi everyone... back from Japan now.

 

In clay bodies I use granite that is everything from fines up to 1/4" to 3/8" rocks.  No seiving.   For glaze material I ball mill the local granite for 6 hours.

 

The clay body grainte stuff is sharp also.  But in a clay body iot does not bother your hands much.  Just don;t bear down on the wheelhead with the sides of your hands!

 

I also use feldspar that I simply crush up with a sledge hammer.

 

best,

 

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

[Biglou13]

Thanks John I've already gotta bag of granite chicken grit. But want to try out some feldspar.

 

I also have a sledge hammer.

 

How do,sledge hammier down the large chunks of feldspar? Do you use some type of heavy bag? Sledge hammer and rocks usually means flying splinters......

[Biglou13]

 

For glaze material I ball mill the local granite for 6 hours.

 

is there a formal name for ground granite,   is there a commercial product similar? 

 

for the most part  granite is    quartz,feldspar with some mica   

 

its part flux part glass...... hmmmm

 

did you just leak one of your secrets?.....

[Guest JBaymore]

Biglou,

 

One of the things one learns is that even if I give you all of my recipes, your work will not look like my work. The particular firing cycle of my noborigama (heating and cooling cycles), the way I mix the materials, the way I handle the clay...... it all differentiates the work. So.... no secrets.

 

One of my stock and favorite glazes is 1/3 ground granite dust, 1/3 seived hardwood ash (unwashed.....mix of mainly oak and maple with touch of birch), and 1/3 local red clay. Wet mixed and seived thru 80 mesh. Glazed on bisque ware.

 

The "name" for the product (if that really is "official") is "granite dust". You can find it (at least here) at granite rock quarries (byproduct of cutting), sometimes places that do graniter counter tops and such, gravestone places, and likely at "garden centers". At garden places and quarries it is gotten in bulk........ bucketloader into pickup truck. I do not know if you can get it "bagged" or not. Never tried.

 

I have a chemical analysis of that granite... because the quarry needs it for the architects and engineers that use the stone for building purposes. Convenient....... I can pop it right into my Insight glaze calc software.

 

As to a "crusher"............... get a short section of 1/4" thick steel pipe that is a TAD larger in diameter than the head of the sledge hammer. Have it cut to a depth that allows the sledge hammer to hit the bottom if you strike down into it. Weld it to a 1/4" steel plate. Put the rock in the container. Hit it til it is the amount crushed you want. Wear eye protection and watch the dust. Outdoors is good. You can also make the "sledgehammer" by welding together a vertical pipe sort of thing that does the same job as a crusher.... and then you can use a deeper piece of pipe for the container.

 

Hope that helps.

 

best,

 

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

[Biglou13]

Friend was up in Montana a brought me some rocks from around custer site. Pink long veins, looks like mica inclusions. Heavy chunk of rock. I'm assuming it's the source of feldspar. I'm planning on crushing for inclusions in clay. A little worried about non feldspar non granite parts of rock. Should this work?

Sure ill test, but getting guest spots in wood kiln is dear, and ends up being a few month turn around, ( yeah my new mantra . Pottery patience )

 

Another thing I'm trying to figure out, sometimes the inclusions cause cracks more often than not? In bisque and in wood fire?

One vase it worked beautifully.

hypothesis is it needs more heat, and work heat to get the melt?

I also think there is a limit to rocks you can add to clay before it cracks?

I plan on refiring, "crack" pieces? Pics to follow