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Found 8 results

  1. So I brought my favorite glaze into class to show my teacher what I was going to do color tests on. Keep in mind she is not a glaze chemistry teacher but she is a very good at teaching throwing & hand building. She quickly pointed out that my favorite tile is full of pinholes. I was astonished. I could not see them at all. I actually thought she was pulling my chain but she was insistent and kept pointing and looking real close and saying "yup, they're there." I kind of wanted to poke her in the eye. I did not. After class, I went home and got my magnifying glass and a flashlight and did a close inspection and there are pinholes. This, of course, made me look at the rest of my glaze tiles more closely and low and behold my very favorite satin color, Cobalt Green, has a bunch of pinholes! Yikes! How did I miss that? and why... why, why, why. I went online and started looking at ways to fix. I'm guessing it's a glaze issue since it only happens with some glazes, not all. If it were a clay body issue it would happen to all. I thought I might try a Satin Matte glaze such as Pikes Purple and switch out the colorants but we all know that will never go as planned. Curious to how Cobalt could be producing such a beautiful Green, I was reading on DigitalFire about Cobalt it mentions that it sometimes causes pinholes. So now I am thinking if I switch out the colorants, not only will that not work, but I'll just have the same issue. Anyway just using the colorants in another recipe would be yet another rabbit hole and I 'm currently thoroughly ensconced in my Hudson River Clay rabbit hole for now. Any Ideas Anyone? Would maybe a 5 minute soak fix this? Here is the Cobalt Green Recipe & Photo. Also attaching a photo f the tile that started all the pinhole hoopla: Neph Sy: 64.8 Spodumene: 13.9 Gerstley Borate: 4.6 OM-4: 7.4 Whiting: 4.6 Flint: 4.7 Cobalt Carb: 1 Rutile: 2 Bentonite: 2
  2. Dear everyone, I am quite new to a slip casting technique. Have made several plaster molds for casting porcelain. And had some success, but recently I have noticed that some of the greenware gets tiny pinholes and then, (because some cups doesnt have it) there are SOMETIMES also pinholes on the glaze. If i got it right, those tiny pinholes are the result of air bubbles or pieces of dust in the casting slip, right? But i wonder, do those pinholes influence the glaze? I am a bit confused, because some of the porcelain cups are not having those pinholes on the glaze and some do have. The thing is that the kiln in the studio where i used to fire my work is very old, and as a kiln technician said, it fires hire than it should and moreover fires unevenly. I wonder if this could be the reason for the pinholes on the glaze surface? Or maybe pinholes on the greenware? Or both? Do you have any ideas? Or similar experience? Thank you in advance!!
  3. I have this heavy blisters and pinholes issue and I m doing the Bisque at cone 08 and glaze temperature is at cone 6 + 40 mins soak., Whats the reason behind this blisters and pinholes ? Is it a clay issue or its something to do with a glaze chemistry ?
  4. From the album: USB Images

    Pin-holing from high feldspar content in clay body.

    © TJA 11-2017

  5. This is a problem I have had intermittently since I started making pottery at home in 2010, and lately it seems to be happening to more pieces each firing. 1. Are these pinholes or blisters? Sometimes they are sharp on the edges. 2. How can I correct this? Helpful (?) details: I am doing a slow bisque firing to cone 04. I hold for 10-15 minutes at peak depending how tight I've loaded the kiln. Bisque firing profile: 80/hr to 250F, 200/hr to 1000F, 100/hr to 1100F, 180/hr to 1676F, 80/hr to 1945. Glaze firing to cone 6. I do a programmed "slow" firing on Bartlett controller to 2167F and hold for 15-20 minutes depending on load. Witness cones show cone 6 achieved. Stoneware clay, made by a local manufacturer (all-purpose Goldart-based body rated cone 6 to 8. Contains 4.5% fine grog). 10 cubic foot kiln, electric Kiln is vented with a Vent-a-Kiln hood that is only 2 months old, replaced broken downdraft vent. Problem occurred with both vents. Trouble occurs sporadically with all my glazes, which I mix. The green glaze recipe in example photos: Rutile green: Talc 5, Custer Feldspar 22 Whiting 4 Silica 26 EPK Kaolin 17 Ferro Frit 3134 26 ADD Rutile (light) 6%, Copper Carb 4% Happens on all types of work: mugs, bowls, etc. I've read on the forum about correcting pinholes with a slower bisque but I feel my firing is pretty slow already. Do I need to slow it more? Why does it only happen to certain pieces? Sometimes two identical pieces glazed and fired at the same time in the same way result in one unblemished piece and one as shown above. Working from home on my own and really feeling out of my depth... and incredibly frustrated.
  6. From the album: Ceramics Fall 2016

    Turquoise stone and white matte ^6 ox on calico dark red clay. A couple very wonky vases that developed decent sized cracks from uneven drying, this was one of the first things I made after taking a hiatus of 3 years from clay, be gentle! I needed to keep a few unsatisfactory pieces to try my experiments. I am totally head over heals in love with the color combo, but am very sad all the pieces developed pin holes on them... I talked to the professor and she is going to go over how to avoid that next time and keep my work together as to have a more consistent firing.
  7. From the album: Ceramics Fall 2016

    Turquoise stone and white matte ^6 ox on bone white clay. A very wonky vase, this was one of the first three things I made after taking a hiatus of 3 years from clay, be gentle! I needed to keep a few unsatisfactory pieces to try my experiments. I am totally head over heals in love with the color combo, but am very sad all the pieces developed pin holes on them... I talked to the professor and she is going to go over how to avoid that next time and keep my work together as to have a more consistent firing.
  8. From the album: Ceramics Fall 2016

    Turquoise stone and white matte ^6 ox on bone white clay. A very wonky bowl, this was one of the first three things I made after taking a hiatus of 3 years from clay, be gentle! I needed to keep a few unsatisfactory pieces to try my experiments. Ended up loving the combo, but am very sad all the pieces developed pin holes on them... I talked to the professor and she is going to go over how to avoid that next time and keep my work together as to have a more consistent firing.
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