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bciskepottery

Akira Satake Kohiki Slip Work (From Going Price Of A Mug)

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A somewhat long missive.  If you get the opportunity to take a workshop with Akira, I highly recommend it.  His workshops are hands-on and he is very generous with his knowledge of technique and craftsmanship. 

 

First, here is Akira's slip recipe: 

Goldart, 6 lbs. (30%)

Kaolin - EPK, 10 lbs. (50%) [Akira also uses Grolleg or Tile 6 for a whiter slip and Helmar for woodfired items]

Custer Feldspar, 2 lbs. (10%)

Silica, 2 lbs. (10%)

 

His recipe makes a five-gallon bucket of slip; I usually half the quantity and make a smaller 2 1/2 gallon bucket.  For the 2 1/2 gallon bucket, I add between 4 and 4 1/2 quarts of water; for a five-gallon bucket, add 8 to 9 quarts.  I generally hold off on the last quart, adding a bit at a time to get the right consistency.  This will be a thicker slip than you are probably used to making -- almost yogurt consistency.  I've found that leaving it a bit on the thicker side and then adding some water as needed is better than making it too thin and watery.  After mixing, it is sieve time (30 or 40 mesh should be fine); this is somewhat labor intensive but the creamy slip you get as a result is well worth the effort.  I let the bucket stand overnight and remove any excess water that rises to the top of the bucket.

 

Recently, I tried using Grolleg instead of EPK and it worked fine; fired a little whiter, which was expected. 

 

For clay bodies, I've used Standard 153 (^10), Laguna Dark Brown (which fires to black at ^10), and Highwater Hestia (^10) that is fired in reduction.  I've played with a couple items at ^6 using Standard 266 and Highwater's Red Rock that is fired in my electric kiln.

 

So, start with a slab . . . either from a slab roller or made by hand.  I use a slab roller because I vary the thickness of the slab just a bit depending on what I plan to make.  For things like boxes and ikebana vases, I prefer a thicker slab to start as it allows for a wider edge seam for joining (I use a 45 degree bevel cutter).  Also, as described below, when you stretch the slabs after the slip firms up, the slab compresses and becomes thinner.  So, you want to allow for that compression at the outset.  I generally set the slab roller for a generous 1/4 inch slab for general items and between 1/4 and 3/8 inches for boxes.  My slab sizes generally run 12"x15" (my slab roller is small); I've found that to be a good size for doing the stretch part described below. 

 

I place a couple sheets of newspaper on a table and then set the slab(s) on top of the newspaper.  On top of your slab, add about 1/3 to 1/2 cup slip.  Glop it in the middle and spread it around evenly -- I use a three-inch spackling knife (you can also use a wide hake brush); don't worry about going over the ends of the slab.  At this point, just try to even out the slip, don't worry about the surface.  (If you want to do some very precise patterns, like the seashell Akira uses on his teapots, use less slip or a thinner slip.)  After allowing the slip some time to settle -- maybe 30 minutes, I go back with a second brush to make my final pattern.  Lately, I've been use a stiff brush . . . a basting brush from the kitchen.  Using that brush, I make my patterns . . . generally just a fluid arm (not wrist) movement from right to left, left to right, starting at the top and working toward the bottom.  You can criss cross or just make parallel lines.  If there is too much slip building up on the brush, remove it and continue.  At this point, the brush lines will begin to develop; work (but don't overwork) until you see a pattern that you like.  If you work it too long, the slip will become less thick and flatten. 

 

At this point, you need to let the slab set . . . I can leave mine out overnight in the studio; how long this takes will depend on temperature and humidity (during the DC summer, it can set in a few hours; during the winter, I've let them set out a couple days in the garage studio).  You want the slab to get about medium leather hard.  Too soft and the slip will not create the breaks you want when the slab is stretched; too hard, the slab will crack and tear.  If the slab does dry faster than you thought, you can use a water spritzer to rehydrate the slab (spritz both front and back to restore even moisture).  If you can bend the slab and the slip does nothing, its too soft; if you bend the slab and it breaks, too hard. 

 

Once the slab is set up, the next step is to stretch it.  This is how Akira creates those beautiful patterns.  For stretching, gently toss the slab across a plain piece of unfinished plywood, 24"x24"x3/8".  First, I drop the slab on the plywood from a height of about 12 inches (just a plain pancake drop). . . this wakes up the clay.  Then I turn the clay over so the slip is face down on a piece of thin foam.  I take a cardboard tube . . . mine are the tubes from rolls of shrink-wrap, about 4" or so in diameter (you could substitute a piece of PVC wrapped in newspaper so the clay won't stick) and if roll the slab around the tube.  This helps break the slip along its texture lines and also begins to give the slab memory of being a curved surface and not flat slab.  [if you are not doing round work, no need for this step.]  Remove the slab from the tube and place it slip-side up on the plywood.  The next step is stretch the slab.  To do this, pick up the slab by the sides and gently toss it -- at an angle -- against the plywood slab so that the slab stretches as it strikes the surface of the wood.  I generally hold the slab in my outstretched arms and toss it at an angle towards me.  Rotate the slab 180 degrees, and repeat.  With each strike against the plywood, you will begin to see the slip stretch and pull away from the underlying clay slab.  Repeat until you get the look you like but don't get greedy . . . too much stretching and the slab will tear or it will compress unevenly.  This is the hardest part of the process and it takes some time to  get a feel for doing.  I've noticed a tendency for slabs to thin more in the middle and tear along the edges if you stretch it too many times. 

 

Once you've gotten this far, your slab is ready and you can make whatever form you want.  If the slab is very pliable, you can let it set up for a while.  For joining edges, Akira uses an overlap technique where he takes a rasp (Sherrill's Mud Tool rasp) and shaves down opposite sides about 1 inch, then scores and adds slip to join.  Basically, you want the thickness of the join to be the same as the thickness of the slab wall . . . if it is thicker, it can distort while drying. 

 

Bisque firing is your usual bisque firing.  Once bisqued, Akira applies a red iron oxide wash to the vessels and sponges off the wash from the high areas of the surface, leaving the RIO to penetrate into the exposed clay body.  I've used straight RIO and water, as well as a combination of RIO, Frit 3124, and water.  Insides are glazed -- he seems to favor shino or iron red, but its really up to you. 

 

Akira fires in reduction to cone 10 in either his diesel fueled kiln.  I fire my kohiki work in reduction in a natural gas kiln.  I've been trying to get a similar look in an electric kiln by applying a soda ash wash to the outside to get a similar sheen on the slip; I'm not quite there yet. 

 

The two keys seem to be catching the slab at the right time to begin stretching, and then stretching itself to get the slip to break and expose the underlying clay body.  When I do kohiki, I'll make 6 or 8 slabs at a time, fills up a 6' folding table top.  Once stretched, I'll store them in a plastic bin, with sheets of plastic separating each slab, to keep them moist while building various boxes, bottles, vases, etc.  The process is a bit time consuming, but well worth the effort, in my opinion.  And, I've adapted and added to what Akira taught in the workshop.  Right now, I'm trying thicker slip applications so the surface is more 3-D feeling. 

 

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Thanks Bruce, terrific post!

 

Question for you, how would you say the pots in this link are done?http://sophiaclayart.squarespace.com/shop/

Her work is thrown. I'm guessing different coloured slips over red clay then scraped off with a wire brush, notched metal rib or something similar then some oxides brushed/dabbed on???

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Thanks Bruce, terrific post!

 

Question for you, how would you say the pots in this link are done?http://sophiaclayart.squarespace.com/shop/

Her work is thrown. I'm guessing different coloured slips over red clay then scraped off with a wire brush, notched metal rib or something similar then some oxides brushed/dabbed on???

 

Very nice work.  Looks like a white slip over dark body, with slip scrapped with various tools, then brushed with oxides (looks like rutile) and underglaze.  You can use an xacto knife to make some cuts in the slip and even peel them back to give a birch bark appearance.  Slips could be built up, several layers of a thin slip.  All slip work and underglaze/oxides done at greenware stage.  Appears to be gas fired, not electric.  A good example (but handbuilt, not wheel thrown) is Eric Serritella  http://ericserritella.com/eric/  .  Another hands-on workshop I can highly recommend.

 

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Love your work Bruce!  But I like the look of Birch trees, to begin with, so I may be a bit biased...

 

Key word is look of birch trees. I have 3 birch trees in my yard. The bark is beautiful. However the actual birch tree is the biggest pain in the butt. It drops leaves year round, along with the leaves you get nice limbs that fall off near winter. The tree loses like 50-60% of its little limbs, and they don't all drop real quick. I go out and pickup limbs and rake leaves almost every day. This morning I picked up over 20 limbs. Freaking birch trees. I am going to eventually cut them down, or sell this house! ahahha

 

anyways, beautiful work!

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Thanks Bruce, nice to hear someone else has thoughts along the lines that I did. Now to just find the time to start experimenting. I've been wanting to break away from the type of work I've been doing for years, hopefully you have just kickstarted it  :)

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Doing these types of surface treatments has really taught me patience.  You really do end up working at the clay's pace/readiness, not yours.  And, for Akira's kohiki slabs, I've mostly given up thinking ahead of time what the slab will be made into as the stretching process reshapes the slab; sometimes you get these really rolling edges that beg to be the lip of a vase, while other times the edges are just plain and boring to look at -- those become boxes. 

 

In our workshop, Eric Serritella said he looked at birch bark but did not use birch bark as a model -- rather, he made his view of birch bark.  The trick is in the details -- using a wire brush to make small marks similar to insect borings in the bark, using a knife to peel back some bark.  I used leather strips for my basket handles; he makes his leather strips from clay -- he carries a couple of rings of clay blends he's made from blending two different clay bodies to come up with different "wood" colors.  And, he will spend 4+ months working on a single teapot or vessel.  That is patience to the nth degree.
 

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Love your work Bruce!  But I like the look of Birch trees, to begin with, so I may be a bit biased...

 

 

Key word is look of birch trees. I have 3 birch trees in my yard. The bark is beautiful. However the actual birch tree is the biggest pain in the butt. It drops leaves year round, along with the leaves you get nice limbs that fall off near winter. The tree loses like 50-60% of its little limbs, and they don't all drop real quick. I go out and pickup limbs and rake leaves almost every day. This morning I picked up over 20 limbs. Freaking birch trees. I am going to eventually cut them down, or sell this house! ahahha

 

anyways, beautiful work!

You see "chore," I see firewood and kindling. Sounds like you need a wood stove or fireplace or wood fired kiln to use it up! :)

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Doing these types of surface treatments has really taught me patience.  You really do end up working at the clay's pace/readiness, not yours.  And, for Akira's kohiki slabs, I've mostly given up thinking ahead of time what the slab will be made into as the stretching process reshapes the slab; sometimes you get these really rolling edges that beg to be the lip of a vase, while other times the edges are just plain and boring to look at -- those become boxes. 

 

In our workshop, Eric Serritella said he looked at birch bark but did not use birch bark as a model -- rather, he made his view of birch bark.  The trick is in the details -- using a wire brush to make small marks similar to insect borings in the bark, using a knife to peel back some bark.  I used leather strips for my basket handles; he makes his leather strips from clay -- he carries a couple of rings of clay blends he's made from blending two different clay bodies to come up with different "wood" colors.  And, he will spend 4+ months working on a single teapot or vessel.  That is patience to the nth degree.

 

Thank you for your detailed post - I could picture every step as you described it. Beautiful work!

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Love your work Bruce!  But I like the look of Birch trees, to begin with, so I may be a bit biased...

 

Key word is look of birch trees. I have 3 birch trees in my yard. The bark is beautiful. However the actual birch tree is the biggest pain in the butt. It drops leaves year round, along with the leaves you get nice limbs that fall off near winter. The tree loses like 50-60% of its little limbs, and they don't all drop real quick. I go out and pickup limbs and rake leaves almost every day. This morning I picked up over 20 limbs. Freaking birch trees. I am going to eventually cut them down, or sell this house! ahahha

 

anyways, beautiful work!

You see "chore," I see firewood and kindling. Sounds like you need a wood stove or fireplace or wood fired kiln to use it up! :)

 

 

Whats funny is I have a huge pile of limbs for kindling on my sheds porch in the back yard. If I pile up anymore its gonna be come a nest for animals. 

 

I used to run a wood stove all my young life. Nothing like waking up at 4 in the morning to load some more wood into the stove. Fun times! 

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The Akira technique is a very specific technique, but as a generality, I'm really enjoying working with slip these days.

 

The thing I like most about it is that it gives you so much control over surface.  Slip applied to leatherhard clay can be manipulated so easily and in so many ways.  For example, one of the oft-repeated queries here is how to make a clean line between a liner glaze and an outside glaze.  If you get your color from slip, it's easy to dip or spray the slip on the outside, and then sponge it off along the rim and inside.  Then you can use a single glaze to get that sharp demarcation.  I also like to comb through wet slip, or carve through set slip.  Lately I've been spraying on several layers of slip in different colors.

 

I've worked out other ways to get richer effects from slip.  I have a deep blue slip that contains fairly high amounts of titania.  When used with glazes that are on the edge of matteness and slow-cooled, the underlying slip affects the glaze enough that the surface over the slip will go matte while the rest of the glaze remains shiny.

 

Anyway, I think slip is a very useful material and probably should be in every potter's skill set.

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I just signed up for his workshop in my area! I was browsing his website and saw he had a workshop in GA this August, it's only 50 minutes from my house! The workshop is only $165 for Saturday(29th) and Sunday(30th)! 

 

http://www.ocaf.com/images/stories/Perspectives/2015Perspectives/p15workshopflyer.pdf

 

I am super excited, first time ever going to a pottery workshop! If any of you people end up going let me know so I can look for you! 

 

WOo Woo Wooooo.. Can't believe I almost missed this. 

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I have been using slip to decorate vessels.  I just use straight clay.  It could use a lot of improvement.  I'm not sure this recipe is right for me, I don't have the Goldart. Can anyone explain what the advantages of using a slip like this verses just clay as I am doing?

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Thanks for the detailed post BciskePottery! Thats why I love ceramics. With just a few ingredients and techniques one can come up with  infinite possibilities. I'll be in Watkinsville, GA this month taking the workshop with Akira. See you in a few weeks Grype!

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I have been using slip to decorate vessels.  I just use straight clay.  It could use a lot of improvement.  I'm not sure this recipe is right for me, I don't have the Goldart. Can anyone explain what the advantages of using a slip like this verses just clay as I am doing?

 

In my experience, a slip made up from stuff other than clay alone can be easier to work with.  I'm using both slips made up as vitreous slips, and plain porcelain body tinted with oxides and made more vitreous with addition of small amounts of flux.  The latter can have problems with flocculation.

 

There are tons of slip recipes available for all firing ranges.  Make up small samples and test with your body-- you'll soon have something that works well for you.  Ball clay is used in many recipes, so that shrinkage will still match in spite of the non-shrinking substantial additions like feldspar and silica.

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Thanks for the detailed post BciskePottery! Thats why I love ceramics. With just a few ingredients and techniques one can come up with  infinite possibilities. I'll be in Watkinsville, GA this month taking the workshop with Akira. See you in a few weeks Grype!

 

Excited to see you there man. Can't wait for this shop.

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