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bciskepottery

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  1. Like
    bciskepottery got a reaction from Julie P in Akira Satake Kohiki Slip Work (From Going Price Of A Mug)   
    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.
     
  2. Like
    bciskepottery got a reaction from Julie P in Akira Satake Kohiki Slip Work (From Going Price Of A Mug)   
    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. 
     





  3. Like
    bciskepottery got a reaction from elaine clapper in Turned Foot Rings On Mugs; Elegance Or Affectation?   
    This might have been posted before, but it is one of my favorite clips . . . Pete Pinnell on cups, how they are handled, and how he judges them.
     
     
  4. Like
    bciskepottery got a reaction from Kilngod ceramics in Akira Satake Kohiki Slip Work (From Going Price Of A Mug)   
    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. 
     





  5. Like
    bciskepottery got a reaction from Bill Kielb in Manganese Dioxide   
    Yes, manganese dioxide is toxic -- both in dry form (breathing risk) and in suspended form (it can be absorbed by through the skin, causing neurological problems). And, your kiln should be vented to outside to remove gases emitted during firing. Lip of a mug is not a good idea as the contact is a point for leeching. Outside of a bowl or mug -- to highlight decoration or make a mark, likely okay; to cover the full surface -- not a good idea. A heavy application is going to go metallic and may/may not completely melt. Will it leech through to inside -- depends. Are your firing your stoneware to vitrification? If not, could be problematic. Are you using a durable, trusted liner glaze? You might see some fuming from your wares to others in the kiln -- are you firing your own kiln or are you risking others pottery in a community kiln?
  6. Like
    bciskepottery got a reaction from LDTarp in temp for opening kiln?   
    For a bisque load, I'll open the top at 130 to 150F.
     
    For a glaze load, I'll prop open the top at 120F and open fully when it gets down to 100F. If it's a cool/cold day (my kiln is in the garage), I might wait a bit longer and let it cool some more.
     
    I fire an electric kiln. I fire with a vent . . . turned on at start of firing, turned off when unloading. Plugs stay in.
     
    At the studio I also use, some have unloaded glaze kilns at higher temperatures . . . to a chorus of "pings" and crazing.
  7. Like
    bciskepottery got a reaction from Bill Kielb in What To Do With Old, Dry, Moldy Clay?   
    A better way of rehydrating your clay is to keep it in its plastic bag and add 1 to 1 1/2 cups water (maybe a capful of bleach in the water in this case 50/50 water and bleach in this case), and reseal the bag with a twist tie. Then put the bag of clay in a 5 gallon bucket and fill the bucket with water until it just reaches the top of the clay block. The water pressure from the bucket will force the water/bleach into the dry clay and rehydrate it. Let it sit in the bucket for a couple of days, or until it is soft and pliable. By not poking holes and filling with water, you eliminate the potential for air bubbles when you wedge the clay.

    I've found mold on some clay just out of the box; it burns out during bisque. I've also had mold grow from recycled clay . . . always figured it was dead cells from my hands, etc. that were decomposing.
  8. Like
    bciskepottery reacted to docweathers in Recommended electric potter's wheel   
    I found a picture of my roller based centering tool mounted on my old M 400. .  The roller is particularly relevant to me since I throw dry.. . Using a variety of other roller based tools that I have fabricated.


  9. Like
    bciskepottery got a reaction from D.M.Ernst in New Teacher ..help!   
    Meeting once per week is a challenge as more challenging/complex projects can't be done in a single period. Choose two or three one class projects, knowing you will need class periods for glazing, etc. Don't think you'll need more than 25 lbs. per student per 8-week class; teach them how to save and recycle scraps.
     
    One clay is best -- otherwise you need duplicate sets of tools, etc; also makes clean up easier. Plus, the red will eventually get into the white clay either on purpose, accident, or other intent.
     
    Most schools fire low-fire. Amaco has a teacher's palette of low fire glazes that work well; you can even mix colors to add to the selection.
     
    Have your projects, but also allow students to play . . . most will tend to make some type of sculpture from scraps, etc.
     
    If a student knows how to throw on the wheel, let him/her. But you are not going to have enough time to teach wheel and you don't have enough wheels for a class to use. I would stick with handbuilding. Here is a good project book to consider -- https://www.amazon.com/Handbuilt-Pottery-Techniques-Revealed-Handbuilding/dp/1438001991
  10. Like
    bciskepottery got a reaction from Pres in Recommended electric potter's wheel   
    I have a Shimpo Whisper VL.  Love it.  Learned on Brents in a community studio that also had some old Shimpos and found the Shimpo foot pedal more responsive.  Direct drive means fewer moving parts to replace down the road.  Had I not gotten the Shimpo, I would have gone with either the Thomas Stuart (pre-bought out by Skutt) or the Bailey Pro. 
     
  11. Like
    bciskepottery got a reaction from Babs in Raku Proposal For School   
    Electric fence with concertina wire across the top . . . and even that is not a guarantee with school kids.
  12. Like
    bciskepottery got a reaction from Roberta12 in Amaco dip/brush glaze compatibility issue ... help!!   
    Can you also get the second glaze in powder form to mix?  That avoids the whole no-gum/gum situation. 
  13. Like
    bciskepottery got a reaction from Callie Beller Diesel in Amaco dip/brush glaze compatibility issue ... help!!   
    Can you also get the second glaze in powder form to mix?  That avoids the whole no-gum/gum situation. 
  14. Like
    bciskepottery reacted to Tyler Miller in Glaze calc the hard way, or, How I learned to stop worrying and love Hermann Seger   
    In my experience, the more technology is involved with something, the further removed you are from the realities of what you're working on.   An example is wood working.  A table saw, router, and screws, removes the carpenter from the nature and feel of the wood.  One upon a time, all carpentry was done with wedges, froes, chisels, planes, etc.  Ripping (sawing with the grain) was unheard of.  You used a froe and riving brake for that.  Items and structures this way are inherently stronger than and superior to those made with sawn timber.  It was the law that parliamentary furniture in the UK had to be made with split timbers until it wasn't feasible to do so anymore.
    I feel the same about glaze software.  Even the best of it tends to be buggy, fussy, and prone to a lot of transcription errors.  I don't find it saves me too much time if I'm serious about a glaze, and I also just enjoy math and being hands on about things.  For this reason, I thought I'd share how I like to do my glaze calculations.  I don't tend to adhere to the usual limit formulae, because they make boring glazes, but in a lot of academic literature, glazes are either expressed as analysis (% by weight) or in unity formulas.  That is, they're useful for replicating effects without being tied to a fixed material set.
    If you get really good, and have a little geological know how, you can actually take mineralogical analyses of chunks of random rock, and formulate glazes around them (or fit them to existing glaze recipes), figuring out how much feldspar, silica, lime, etc are in the rock.
    So this is how I do glaze calcs, with just a periodic table, some chem. knowledge, a pencil, paper, and an antique solar powered calculator.  The info I've presented here comes from Digitalfire's discussion of unity formulae, Linda Arbuckle's discussion of the same, and Michael Cardew's Pioneer Pottery.  All present basically the same stuff, but I find each presentation a little opaque in its own way.
    I'm going to keep things simple, and I'll start with a theoretically pure mineral to keep the math convenient and short.  Let's say we have the following analysis for a feldspar:  SiO2: 68.74% ; Al2O3 19.44% ; Na2O 11.82% .  Theoretical soda feldspar.  To be any use in calculation, we need to convert this to a unity formula.  Hermann Seger was the first to express things this way, and it's based on the theoretical K-Spar formula 1 K2O. 1 Al2O3. 6 SiO2.  The idea is that all the ROs and R2Os add up to 1 and the rest are expressed in terms of this as a ratio.  But, this is expressed in terms of numbers of molecules, not molecular weight.  So we need to figure that out.  Period table time.  I'll do soda and just give the rest.  Sodium has an atomic weight of 22.9898 g/mol, oxygen 15.999.  There are two atoms sodium, one of oxygen, so that's 2(22.9898) + 15.9999 = 61.9796.  The molecular weight of "soda" is 61.9796 g/mol--we'll knock that back to 61.98 to keep the math nicer. I should add that a mole is a fixed number of atoms or molecules.  Alumina's molecular weight is 101.96, and Silica's is 60.08.  Knowing this, we can say the percentage is a portion of a 100 gram sample of the feldspar.  So, 68.74/60.08 = 1.1441.  There is 1.1441 mol of Silica in our feldspar.  11.82/61.98 = 0.1907.  There is 0.1907 mol of Soda.  19.44/101.96 = 0.1907.  There is 0.1907 mol of alumina.  To get the unity, you would add up all the fluxes (RO's and R2O's) and divide each individual flux by the sum.  There is only one flux in my example, but if there were two or more (as there almost always is), you would add up all the molar amounts and then divide each by the sum.  Like, if there were 0.2 mol CaO and 0.1 mol Na20, you'd add those to get 0.3 and then divide both to get your unified fluxes (0.66666 Ca0, 0.3333 Na20).  But, since we just have the soda, we just get 1.  Then, we divide the silica and alumina by the 0.1907 (our sum of fluxes).  We get 5.999 Silica, and 1 Alumina.  The formula for theoretical soda spar: 1 Na2O. 1 Al2O3. 6 (ish) SiO2.
    Then, we want the formula weight.  We multiply each by its molar mass, and add the products.  61.98 + 101.96 + 5.999 (60.08) = 524.35992.  We'll call it 524.36.  Note that Tony Hansen is a little off this, because, I think, of a transcription error.
    Ingredients that are pure flux, like limestone, are just a 1.  The one exception to this unity is kaolin, which is expressed in terms of "ideal" kaolin, 1 Al2O3. 2 SiO2.  The actual formula is something like 1 Al2O3. 1.996 SiO2
    But now we have all the info we need to make a glaze.  In this case, a 4-3-2-1 cone 8-10.  What I call "toilet bowl clear."  40% spar, 30% quartz, 20% limestone, 10% kaolin.
    Make a chart, with the materials down one side, and the ROs, R2Os, RO2s, and R2O3s all expressed across the top, like below.  Divide each percent by the formula weight, to get the equivalent weight.  And then multiply the equivalent weight by each member of the unity formula.  Plug the product into the relevant box.  For the soda feldspar, this means 1 x 0.07628 for the Na2O box, 1 x 0.07628 for the Al2O3 box, and 5.999 x 0.07628 for the SiO2 box.  When you have all the relevant boxes filled.  You do the same unifying procedure as you did above.  Add all the fluxes together to get a sum, then divide each flux by this sum.  We get 0.27628. And 0.2/0.27628 = 0.7239 (CaO), then 0.07628/0.27628 = 0.2761 (Na2O).  These total 1 for unity.  Then 1.036/0.27628 = 3.75 (ish) for SiO2.  And finally 0.4188 for Al2O3.  So our unity formula is CaO: 0.7239; Na2O: 0.2761; SiO2: 3.75; Al2O3: 0.4188.  Which ain't bad for a cone 10 glaze according to established limits.  Our "toilet bowl clear" glaze should be a success--according to the math, at any rate.
    This is a grossly simplified example, but I encourage you to seek out this info on Tony Hansen's site, and anywhere you can so that you can use a pencil and paper to do this on your own, with your own numbers.  Even if you do it only once.  It will help your understanding of glazes immensely.  And you can seriously use anything you have an analysis for to make a glaze.  Get a rock analyzed and go from there.  Math and Science are fun!
     
     
     

  15. Like
    bciskepottery got a reaction from glazenerd in Is Patsy Green 2 From Britt Book Food Safe?   
    Whether 1 foot x 120 feet or 15 feet x 120 feet, they are all billable hours.  And the more lawyers involved, the more hours billed. 
    (Full disclosure:  my daughter is a law school graduate, I work with an agency full of lawyers, and am a consultant who bills by the hour.) 
  16. Like
    bciskepottery got a reaction from Joseph Fireborn in Saving your hands.   
    Needless to say, a tetanus shot (or booster) is never a bad idea for those working in studios.  After the needle tool, the metal flexible ribbon of death (your shiny metal rib) is the next most dangerous item of which to be wary.  (Yeah, bad pun on needless)
  17. Haha
    bciskepottery got a reaction from glazenerd in New Forum   
    Click on your user name
    Then click on "Account Settings"
    Then click on "Notification Settings"
    I cleared all defaults and clicked on "no notifications" option
    Then click on Save button before returning to forum.
    Hopefully that would do it. 
  18. Like
    bciskepottery got a reaction from Achilles in Kiln Wash Ruining My Work   
    Regular bisque temp for calcining should be fine.
     
    The purpose of calcining is to remove chemical water; by doing that, it will shrink less upon drying.
  19. Like
    bciskepottery got a reaction from Joseph Fireborn in Stacking Pots Rim To Rim In Glaze Firing   
    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.
  20. Like
    bciskepottery reacted to Dick White in Moon Jars - What Are The Rules To The Form?   
    I read the PMI article about using the pipe fittings, and being a cheap SOB, decided I could do the same for free. Get a large plastic soft drink cup (7-11 Big Gulp or similar) or a plastic food container that has a mouth just big enough to comfortably slip your hand through, and which has a rolled over edge for a rim. Cut the rim off the cup about 1/2" down, being careful to not damage the rim. It may take several successive cuts, first with a knife to cut a larger piece off the cup, and then scissors cutting around and around until you have a plastic ring. Smooth up the bottom cut edge with some sandpaper.
     
    Now throw a tall cylinder, the top of which has an inside dimension that exactly fits the plastic cup rim ring. Slip the ring down into the cylinder and gently collar it tight onto the ring. Now you have a strong support to keep the rim of your cylinder perfectly circular while you belly it out into the moon jar form. Use your heat gun/torch/etc. or not as you wish. When the form is basically complete, gently lift the cup ring out of the cylinder, or if necessary, use a needle tool to cut just enough of the rim to remove the ring. Now finish the rim as desired.
  21. Like
    bciskepottery got a reaction from pmeredith in Bottoms Chipping During Firing   
    It is called plucking, often happens with a porcelain or a porcelaineous stoneware. From your description, it sounds like you do not wax bottoms. That could be a first step. Or add some alumina hydroxide hydrate to wax -- the alumina in the wax will help keep the wares from sticking to the kiln wash. Or, use wadding.
     
    Edited 5/12
  22. Like
    bciskepottery got a reaction from oly in Michael Cardew Techniques?   
    Here is a video of his son Seth demonstrating brushwork.
     

  23. Like
    bciskepottery reacted to Mark C. in Totality=One Lucky Guy   
    I was lucky enough to have 4 days to travel and find the perfect spot to shoot the eclipse.
    We had booked our hot springs hotel 2 April's ago and had 2 full days to scout out the perfect spot.
    one that was free of obstructions and crowds preferably out of the smoke f the three forest fires burning around us in the cascades.
    Since the smoke was a wait and see that early am we picked our three spots a-b-and c
    A was 5,000 feet and off the road on an unmarked road about a 30 minute drive from the hot springs-totality-1.5 minutes
    B was 45 minutes away on a off road theta was super narrow on the way to a boy scout solar camp on top of a hill-1.3/4 minute totality
    C was 45 minutes away on the side of the road on a wide pull out-2 minutes of totality
     
    We got rolling at 6 am and choose the A spot as it was deserted and smoke free with about 200 degree view-as we where hoping to see the shadow race by.Later another truck showed up to watch from this point as well
    3 years ago I bought a 300mm to shoot bears (take photos) in Alaska on a friend's invite who used to guide and lives in Homer.
    I have about 5 tripods and 3 camera bodies so I set up a few cameras and shot mainly with my 300mm matched with a teleconverter 1.x4 so my lens was about 672mm long.
    I used a shutter release and programed the camera to bracket 9 shots in a quick succession that takes about 3 seconds. I set the aperture at f16 and the bracketing changed the shutter speeds with 9 speeds in rapid succession .
    I bought a 77mm firelight solar filter that steps the light down 16 stops and is a 100% must for shooting any sun photos with any lens . This filter you remove during totality and put back on when the diamond start (sun appears again)Without the sun in lens you cannot see anything thru the filter-its completely dark like your solar glasses where.
    I spent 1/2 a day practicing on Sunday and reading my manuals and the articles on how to I printed and brought with me as we where out of internet range-cell phone range or any other range.
    I have shot moon eclipses and played with some solar annular s about 5 years ago thru my wielding glass with lesser cameras with some luck.
    Of course I made a shadow box to view during the sunny phase as I always have since a kid.
    With this deal you never know what or how it will turn out-luck may or may not be your friend-you practice as the seconds count  by and you also really need to enjoy it yourself so you need a few seconds without camera stuff to bog down the moment.
     
    As it turns out I shot 488 photos of the event and most came out great
    I captured all the 4 phases got shots of Baily's beads and the diamond ring along with the solar corona around the sun and light rays galore.
    I'm feeling like one lucky guy really as his could just as easily been a bust
    here are 4 of the 488 shots
    Phase one
    then Baily's beads
    Totality -corona
    and the diamond ring effect
    Now it back to clay production and more grounded activities.
     




  24. Like
    bciskepottery got a reaction from preeta in 100 Sake Cups   
    Can we assume you will test each cup to make sure they work properly?
  25. Like
    bciskepottery got a reaction from Joseph Fireborn in 100 Sake Cups   
    Can we assume you will test each cup to make sure they work properly?
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