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susieblue

Sodium Silicate Alternative For Throwing Technique?

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I have become somewhat interested in the technique of creating texture on thrown pots using sodium silicate. i am curious to know if anyone has ever tried to use other materials to create a similar effect?

 

I know it's easy to order the stuff online (when freezing isn't a concern) and I could make it myself from lye and desiccant. Just wondering if there is any other readily available liquid that offers a similar outcome. (I suppose I am being a bit lazy, too - who really wants to run out to Walmart when the temps are in the single digits, there's 2 feet of snow on the ground and the driveway's coated with ice?)  

 

Thanks.  :)

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Guest JBaymore

But the torch does not do the same exact stuff.  Can do some things similar.... but not the same.  And I've found a heat gun works better than a torch for THIS effect; dries the surface more rather than fully thru the cross section.

 

Try any defloculant.

 

best,

 

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

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I threw this a few days ago and applied slip mixed with some sodium silicate. It is still in the greenware state. I used a hair dryer for the exterior surface. The only difficulty I've been having with this technique is stretching it evenly around when only pushing from the inside without any outside support. The walls of this piece are a little thinner than the past ones I've made and they drooped a bit while it dried. I keep trying and learning more with each attempt because I love how these look.

post-61902-0-37614500-1423091253_thumb.jpg

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What you are looking for is a substance that will form a thin "crust" on top of the surface that, after being heat dried, will crack as it is expanded from the inside of the pot.  Maybe a thin wash of Caro syrup might work?  Might be other substances, too -- liquid floor wax?  Just suggesting, have never tried. 

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Guest JBaymore

The sodium silicate works because it "kills" the outer clay layer's plasticity by changing the chemistry of the water in that layer of clay.  The part it can't migrate into (interior of the form) remains plastic.    it is not that it dries.  With sodium silicate... there is no need to use a torch, heat gun, or blow drier.   You CAN use them... which changes the effect somewhat.... but you don't have to.

 

best,

 

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

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Susie: You can also try to cut (not deep) lines in the cylinder surface with a knife. Regular lines or irregular lines, criss-cross, whatever, and then belly it out from the inside (no touching the outside!). You will get similar "cracks".  Welcome to the forum!

 

John: I didn't know you don't have to dry the sodium silicated surface before bellying it out... have to try that. Thank you!

 

Evelyne

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Guest JBaymore

John: I didn't know you don't have to dry the sodium silicated surface before bellying it out... have to try that. Thank you!

 

For me it is heavily about the TIMING of the application of sodium silicate.  The longer it is left on the piece the more pronounced the cracking of the clay as the sil penetrates deeper and deeper into the clay body's cross section.  And different bodies have a different level of "openness" to the penetration of the liquid in a certain amount of time.  So the amount of time that it takes on one particular body might be "too much" or "too little" for a different body. 

 

Also the WAY you apply the sil matters.  Try different application techniques.

 

I was doing a demo of this approach with the silicate at Tokyo National University of the Arts a number of years ago and a number of people from China (PRC) who were there were fascinated by this little "trick" I was using.  Apparently they had never seen it. (Which surprised me a lot.)   That demo and 'crossing of paths' resulted in me getting published in a book in China talking about that ;) .

 

best,

 

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

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Glenn Woods teaches this technique at the Dunedin Fine Arts Center in florida.  he uses a heat gun.  check out the facebook Potteryboys for examples of his beautiful results.

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John: thank you very much for this additional info. You say "the longer it is left... the more pronounced..." Do you mean: the longer it is let before bellying out? What would you say is max.? Can I throw a cylinder, apply sodium silicate and go have a coffee or two? If I leave it long enough, can it penetrate the wall of the cylinder? (I throw thin walls).

 

I apply it with a thick brush (what else?? :blink: ). What I don't like is that it's always running down the cylinder and onto the wheel head. If I don't wash it away immediately, and take the hair dryer to the sil, it sticks on the wheel head and I get nasty permanent stains. Even when I use it without additions of oxides etc.

 

Good for you being published in a book in China!

 

Evelyne

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Guest JBaymore

Evelyne,

 

Try different stiffness and sizes of of brushes.  Try different patterns of brush strokes.  Put it on very unevenly.  Don't put it on everywhere.  Lightly rough up the surface before applying the sodium silicate.  And so on.

 

As to the timing business, the standard correct answer to ANY question in ceramics applies here as always" "It Depends!"  ;)

 

Cylinder thrown... outer surface prepped for the sodium silicate.  Apply the sil.  Then wait X seconds/minutes.  Belly out.

 

I typically leave if for anywhere from maybe 30 seconds to as much as a couple of minutes, depending on what surface I am looking for.  Could never got get a cup of coffee.  I am constantly watching the surface and the amount of water coming out of the wall.  It is a 'monitored process'......I'm right there, in the moment, watching.

 

I throw dry (slurry or nothing) and thin too....so have to be careful with the timing.   Too long and yes... the piece will crack right through.  (If you throw thicker...... this might never happen... never tried.)

 

When I am doing this I have a stock of tissues/paper towels sitting on hand.  The sil goes on.  Then with the wheel rotating very, VERY slowly I use the tissues to simply sop up the mixture of sodium silicate and water (being driven out of the clay body by the change in the ability of the clay to hold the water) and throw them away.  I also immediately am using a small sponge with water in it and running that along the wheelhead to get the crap off there before I start bellying.  (NOTE:  don't throw the tissues on the table or floor around the wheel.... as it dries sodium silicate is a GREAT glue!)

 

If I am using a wood bat on the wheelhead, it is a bat that is solely for using sodium silicate.  Eventually it screws up the absorbtion of the bat surface.

 

Hope that helps.

 

best,

 

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

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Ah John, yes of course it is helpful. Thank you so much for all your time and all the information. You know I have a "John"-file on my Computer and I copy/paste your knowledge on everytime I see you posting? It's quite long already :)

 

(whisper - you'll get a hug from me in Providence!)

 

Bummer! I'am out of "likes" once again. Sorry John.... ;)

 

Evelyne

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