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Posts posted by bciskepottery

  1. Unless you apply alumina to the rims, they are likely to stick during a glaze firing (unlike a lower temp bisque firing).


    Understand the desire to maximize kiln space, but work with what you have and focus on quality, not quantity. Cost of electric firing is not that much in terms of overall price of an item. May be a few pennies more per piece now, but you'll make it up later with larger kiln.


    Think long term, pottery/ceramics is not for those who tend toward instant gratification. But you already knew that -- as evidenced by your journey so far and your work to achieve your own voice in glazes, etc.

  2. Gas bubbles in the 266. The glaze is maturing and sealing the surface before the gas bubbles from the clay body are released. Most common remedy is to hold top temperature during bisque to allow more of the Sulphur and other impurities to burn out. Also, stack the 266 loose in the bisque to maximize surface area to promote burnout of impurities.


    Not an uncommon problem with 266 and similar clay bodies.

  3. Depending on how wet or dry you throw, you tend to lose the fine particles of clay in your slop.  When recycling, you need to restore those fine particles or the clay becomes stiff/hard to throw -- potters use the term short to describe the clay.  By adding your slop to the recycled clay (see Marcia's post), you restore fine particles and the clay keeps more of its plasticity.  If you don't add back your slop, you need to add a fine clay to the recycle clay. 


    Given Coleman is a bit pricey, save your slop and recycle your own . . . don't mix it with the others.

  4. I've used the Mayco SW002 clear satin matte with good results on exteriors of ikebana vases.  It was applied over black underglaze and oxide stains used to highlight texture.  Clearness will depend on application and thickness -- whether satin, matte, or glossy. 



  5. OH!  Just make little balls of clay and put them underneath?!  What fun!  How far apart...I'm guessing about 1 inch apart...so 8-10 for a platter with about 4-5 inches diameter  flat area on the bottom?


    ( I love the interest in this, and the advanced scientific discussion some of you have brought into it!)


    Not little balls of "clay"; little balls of a mixture of 50% alumina hydrate and 50% EPK.  For a platter, five -- one in each corner and one in the middle.  Roll the wad and attach to the bottom of the pot with a bit of Elmer's glue.  When attaching them, avoid touching other areas of the pot with the hands/fingers used to make/attach the wad as any transfer of the alumina could result in a white spot where you touched.  I usually keep a damp hand-towel nearby and wipe my hands between placing the wads on the pot and then putting the pot on a kiln shelf.  Left over wadding can be kept in an airtight zip-lock bag; some keep theirs in the refrigerator/freezer if the wadding includes organic materials (in salt kilns, some add sawdust, flour, and other organics to burnout of the wadding and make it easier to release from the pot; I generally use the 50/50 mix and have not had problems with sticking).

  6. The mindset in the U.S. is that if it contains any trace of lead, customers will walk away from the item. And, one of their first questions will be, Is the glaze lead-free. Even though there are permissible levels of lead allowed, even though you might only put it on non-functional wares or non-food surfaces, even if the lead is encapsulated or fritted -- if it has lead in it, customers will walk away. It is that simple. They know to ask about lead, maybe not to ask about barium, manganese, and a few others.

  7. My Ceramics monthly for October seems to have arrived early. In the back they have an article on Ian Currie and his grids so maybe more people will be finding this topic.


    Not as long as we continue to see the proliferation of commercially prepared glazes that imitate the look of shinos, celadons, etc. without the work of this type of learning/experimentation. 

  8. Maybe one of these will work . . . https://www.google.com/search?q=fingerprint+brushes+and+powders&tbm=isch&tbo=u&source=univ&sa=X&ved=0CCsQsARqFQoTCPLLmuaLz8cCFccXPgodEV0EWA&biw=1600&bih=698I've not tried them, but they might be worth a try. Apply dry black mason stain to the fingerprint dusting brush and then dust the feather area; may take some practice to get the application right and you could always use a paper or flexible plastic outline of the feather to prevent stain from getting on adjacent areas. I think apply to greenware would offer the best luck for success as the dry stain would adhere to the damp surface and you then bisque the stain before applying glaze over it later. Plus, Mason stain has frit in it so it will be less likely to smudge after bisque firing. After bisque, you could also lightly sand any stain that got in areas outside the feather.


    Applying fingerprint dust (or mason stain) is an art, a little dust goes a long way.


    And, if you try this, be sure to wear an appropriate protective mask.

  9. 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.

  10. 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.




  11. 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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