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Found 11 results

  1. Hi! I have been making pots for about 7 years and in the past 4 have struggled with small s-cracks appearing on the bottom of about 75% of my pots. The s-cracks are usually around a half inch long, thin, and only on the underside of the pot - never go all the way through and therefore the pots are all fully functional, just annoyingly cracked. In the photo attached, you'll see 3 cracked pots, and 2 planters that did not crack. My theory is that something is amiss in the center of my pots that causes stress & cracking during drying - because typically, when I make planters that have the centers removed, cracks do not appear. The cracks don't show up to my knowledge til after the bisque fire (though because my studio fires my pottery, there are usually a few days that I'm not seeing the piece before it's loaded in the kiln.) I have tried just about every remedy I can get my hands on and still can't manage to kick these cracks to the curb. My current regimen is: 1. Wedge each piece of clay (ram's head) 40x each. 2. Align clay on wheel so the spiral-y part is horizontal per this video: https://www.youtube.com/watch?v=f7oIZiXmXFU 3. Tap clay to center and use a finger to create a seal between clay and bat. 4. Add water, press down on the clay and get into flat hockey puck-ish shape. 5. Cone up and down three times. I make sure my cone is very cylindrical, with the bottom being almost as narrow as the top, which I read was important for preventing cracking. I make the top of the cone teeny-tiny and focus on getting air bubbles out of that portion. 6. During coning down process, I bring the piece back into a hockey puck shape and run my finger across the top towards the center, occasionally finding air bubbles there. 7. Bring out the walls and compress bottom religiously with my thumb, a kidney rib and my sponge. About 10 times, compressing from the outside of the base to the center. Occasionally, I'll feel little air bubbles during this step and will continue compressing until I've popped them. 8. Continue to compress and flatten bottom as I shape the piece. I don't let water sit in the piece. 9. Let the piece dry slowly and evenly on absorbent surface like canvas or foam (covered after a few hours). Dry with bottoms up once sturdy enough to stand. Something I've noticed: Often when I use the wire to take pieces off the bat, there is a small air pocket right in the center of the clay that appears both on the remaining clay on the bat (picture attached), and on the piece itself. The indentation in the bottom center of the piece is never more than 1/16-1/8 of an inch deep I'd say. It's something I trim off later in the process, but seems to correlate with the pots that end up cracking. A hypothesis: Could I be creating these air pockets during the coning up process? I.e. as I press the clay in & up the bottom air pocket forms? Maybe making my cone so cylindrical is part of the problem? Another potential hypothesis: My wedging is bad and introduces too many air bubbles. Would I be better off using clay straight from the bag? (Or, sigh, trying to get better at wedging?) Last note: I prefer a flat bottom to a footed bottom. It's possible I get less cracks when I trim feet, but I haven't really investigated. Any advice you have on ending this years-long struggle would be so, so appreciated! S-Crack Photo Bat with Air Bubble
  2. Hello Community! :-) I am pretty new to ceramics and I am learning new things about this fantastic material on a daily basis. For my latest project I am trying to crack/break up old clay bottles with the principle of the heat shock. Does anyone have an idea what would happen, when I rapidly heat up a bottle (like the one in the picture) to 1800 degrees Fahrenheit ? My wish would be to let the bottle explode and to create many fragments. Is the wall of the bottle maybe too thick (approx. 4mm) to really burst into pieces? Will nothing happen or maybe just one big crack? Or does anyone have an idea how to make the shock/explosion bigger ? Thank you so much for your help!
  3. Does this crack in the firebrick in the lid of my kiln need some kind of attention? I've been told both yes and no. It's a Shimpo DUA-15 kiln. Bob
  4. Hello! I have recently made the transition from earthenware to stoneware to create mugs and dinnerware. I am fairly confident I applied the glaze to thickly to these mugs as I have made three and all three have small thin hairline cracks around the areas of thicker glaze... bummer.. a lesson learnt. I wonder if i can save these mugs though? The cracks are only on the outside surface there are no cracks to the bottom or inside. Shall I write them off (use might be dangerous) consider them seconds or try to repair the cracks? I have seen a few methods of repairing on google, I don't want the repairs to be too obvious, Would be nice if i could repair and re-glaze to blend the appearance of the repair. Any advice would be greatly appreciated, I may be a little sentimental over these as they are my first function stoneware makes.. Emma
  5. So, I need a crack expert. I have a piece of cone 6 porcelain greenware that keeps cracking when it drys. I've repaired it numerous times, dried it for weeks, wet the entire piece down, nothing is working. It's a small crack on the edge of the piece. 1 cm maybe. I can not make it again, I need to fix this crack. Help me please!
  6. So I pulled this out a bowl this morning and found a 1" crack. I did not see it after bisque - and I looked. How / why did this happen, any ideas? Can I grind it out and reglaze maybe? I don't see it on the back but when I fill it with water it slowly dampens the surrounding area. Thanks
  7. Judy_in_GA

    lilypad2

    From the album: Handbuilding work

    This lilypad plate is for under a frog planter I'm working on. It developed a small crack on the back during bisque however I wanted to test the glaze so went ahead and glazed it. The crack came to the front and lengthened during glaze firing but I really like the glaze. This was a slab rolled piece, handcut then embossed using one of the large ball Sculpey embossing tools .. I love those things! Other than the crack I'm really happy with this so I'll remake for the frog planter.
  8. Hi, I slip cast my work using low fire clay. I fire three times, Bisque and glaze at cone 05 and decals at cone 010. I am having problem with one particular slip casted platter consistently. In third firing (cone 010) this style develops hairline crack. Not all the pieces develop the crack but lately 3 out of 4 have, which implies I am doing something wrong, but I am not able to figure out what? I glaze the whole platter ( inside out) balancing it on triangular firing stilt and they are fine after glaze firing. It is the last cone 010 firing for decal that the crack appears. As the crack is not sharp and glaze seems to bend inwards I gather it happens at the early stage of firing. Please advice.
  9. I bought a third-hand kiln recently, which has some substantial cracks in the floor, as well as the remains of a number of glaze runs. It's a Paragon TnF-82, so it should be possible to turn the bottom over. However it looks like some of the cracks may go all the way through, so I'm worried that it'll fall apart if I try to flip it over. I'm not in a position to replace the floor right now, so is it best to leave it as is? In another thread, Mark C mentions that he puts his kilns on a thick piece of sheet metal to support them better. Would it be worth doing this for my kiln, given that it's only about 65cm in diameter? On the other hand, the support that came with the kiln looks like it could be a bit bigger.
  10. Hello everyone, I have some cracking/breaking issues after glaze firing and i would like to discuss it with someone who had similar problem. I slipcasted the pots (lots of them), than bisque fired them, after glazing, fired again. After the kiln cooled down loaded off the kiln than the pots began cracking, breaking one after another. Even a day after they're continuosly breaking. I've already made a 100 of them about a year ago did everything the same and i don't know what went wrong this time. Could somebody give me some advice in that concern? Thanks & regards Lorraine
  11. I have a question I hope those if you that use it can help answer. I have a sculpture that took me over a week to make and almost month to dry slowly. I was getting ready to paint on the underglaze decoration when I noticed a very fine hairline crack across the tip of one ear, all I can think is it got bumped at some point and I didn't notice it. I whipped up my first ever batch of Paperclay Slip, thank you everyone for posting your recipes! I used toilet paper, some of my dry clay body, a bit of water and some vinegar to make a thick slurry. I brushed this on the ear inside and out in several layers allowing it to dry in between. Now that it's dry can I clean it up and paint underglaze on it like I was planning to? Or should I gently clean and smooth the area bisque it THEN paint on the underglaze? Thanks for your help! Terry
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