Monday, October 20, 2008

Fresh Out of the Kiln

At this point in my life I want to know a lot about clay in a relatively short amount of time, which isn't always possible, but that doesn't keep me from trying. We just unloaded the kiln this evening. From my perspective, I am progressing and learning a lot and the evidence is shown in this glaze firing.

Here you see one of my shell bowls made from Windsor porcelain clay with a beautiful blue glaze. I really like the way this glaze pools at the bottom and I also like the shape of the bowl. Windsor porcelain is a joy to work with in hand building. The clay accepts the glaze nicely and is a good fit. However, the glaze ran a bit at the bottoms of these bowls and will need to be ground down some. I have a set of four of these bowls and one cracked being removed from the kiln shelf.

Here you see the same form shell bowl made with Black Mountain clay with a painted fish under glaze and a transparent over glaze. This is the first time I have used under glazes and I have many more ideas to try with these types of glazes. The transparent glaze over the top has reacted with the iron in the clay body to produce an overall gray or gray-green background color which was not what I was after. I wanted the black clay body to show through.

I am not sure it is possible to achieve an actual clear glaze over a black clay body in a reduction firing. I have one more transparent type of glaze to try that is supposed to be good over oxides, not sure it still won't react with the iron in the clay body to produce the gray tones again. We shall see in the next firing.

If you recall our last glaze firing didn't achieve Cone 9. Here are the cones from this firing. The cones pictured on the left were on the next to the bottom shelf of the kiln and are probably almost Cone 11. The cones on the right were on the top shelf of the kiln and are not quite to Cone 10. We have a discrepancy between the top and bottom of the kiln tempratures and consequently glaze maturation varies from the bottom of the kiln to the top.

In previous posts I talked about my experimentation with platters and plates, I've been striving to achieve a good form from a slumped or humped mold without having the plates or platters warp. For this firing I achieved some successes and failures in that regard. Here is a new square form with four undulations and no foot, this form seems stable and didn't warp at all. The transparent glaze was supposed to allow the blue under glaze to show through, which it did. The transparent glazes was also supposed to allow the black clay body to show through, but again has reacted with the clay body to produce more of a grey tone and has obscured the color of the clay body. I think the transparent glazes are going to take much more experimentation.

This round porcelain plate is made from Windsor porcelain with a blue and salmon under glaze and celadon glaze over the top. The plate was constructed with a slump mold. The plate did not warp and was placed on the kiln shelf with porcelain sand underneath. I wish I had put a border design around the outer edge of the plate. I also want to practice more with under glazes, but I like how the color blended ever so slightly and the celadon almost acts like a clear over the under glazes.

I had high hopes for this medium square platter since I took quite a bit of time formulating, measuring and painting the semi-circle under glaze design on the platter. Here again I used Windsor porcelain on a slump mold with a flat bottom and no foot. Although the platter didn't warp, it does have a large crack on one side. I'd like to try this platter and this design again as it is one of my favorites - a semi-circle design on a square platter.

Previous crosses I have made have warped due to hanging attachments I placed on their reverse. With these next two crosses I left off the hanging attachments and they didn't warp. I will probably be attaching a metal hanger with epoxy to the back of these two. Although I did impress in a nail recess on the upper back, I am not sure that will be sufficient to hang them safely from the wall without risking their falling.

Stay tuned to see more from this firing in my next post where you'll see an unusual pinched and sculpted bowl, yarn bowls, free form bowls, and other bowls with some unique glazes.


  1. Great work from your firing. What kind of kiln are you firing? - did you build it yourself? - have you been firing gas/reduction for a long time?
    I'm trying to decide if I want to stay at ^6 oxidation or work toward building a gas or salt kiln.

  2. yeah, things do look great!!!! EXCITING!

  3. Hi Judy, I have been doing cone 10 for three years at the college. It is a West Coast kiln we use there. Here is a link We use natural gas. As I understand, propane is harder to control, be sure to get a large enough propane tank if you do as the pressure in the tank drops when you draw lots of fuel from it and can affect your firing (fluctuating the temperature too much).

    We have three of these kilns at the college, they are old ones - not sure how old. Only one is still programable, and one doesn't work at all, but they are actually pretty easy to use. We do both our bisque and glaze firing in the gas kiln. We usually candle for two days for the bisque because of the varied student work (to prevent cracking and blow ups).

    For the glaze load we warm it up, sort of a semi candle and then start bringing it up from about 9:30 am to about 7 pm and then shut it down. For this load we did heavy reduction about the last 3-4 hours.

    In my next post you'll see some more from this firing with some other great results. Reduction is fun when it turns out, but the pieces don't always turn out the way you think they will, especially when we have so many different glazes all in the same load. And the piece next yours in the kiln may have a completely different glaze on it and it can do some jumping over, etc. (at least that's what I call it).

  4. Hi Gary, thanks, there's more to come as soon as I get the photos taken.

  5. Linda - thanks for all the info. I have access to the gas kiln where I'm an apprentice. I get a free class each session & put the pots I make in class in that kiln. I've worked really hard on my ^6 ox. glazes & don't want to be lured by the sweet gas kiln so I try not to get too excited.

    It will be a year or so before we can move. I can't have a gas/salt kiln in my neighborhood. But I'm always wondering if it's worth the learning curve to try gas when I set up a new studio. (We're thinking of moving on some land when my son moves out).

    I love your work & looking forward to seeing more.

  6. Thank you so much Judy - I'm really just beginning in ceramics having just taken three semesters of ceramics over the last three years. But I have been reading everything I can get my hands on, taking workshops, and working at the school many more hours than just my class time. I want to move so I can have a larger studio with room to expand and for everything I have collected. If only the housing market would pick up.

    Since you already know clay and Cone 6 glazes, reduction glazes would be a snap. You could start by using commercially prepared glazes or use other people's glaze recipes and then tweak them or adapt them to your own use while you are developing your own glazes. That way you will have some glazes you can depend upon so you can keep up your production with a nice look. I understand there are some Cone 6 glazes that can give the "look" of reduction glazes and I am planning on working on those next with my kiln here at home. The cost of a gas kiln is expensive and the cost of fuel is probably much more expensive than electric so that is something to consider. But you could also charge to do firing and give classes to others to recoup some of the costs.

    Your Cone 6 glazes are beautiful and not like anyone else's - if they were mine I'd be very happy with them but I understand the desire to learn and do more in clay - it is so addicting.

    Any you can always have both gas and electric firings and glazes too when you move.

    I hope to one day build one of those manabigama kilns (fires in 8 hours) when we move. I forget who back East built one - oh heck I looked in my notebook - its John Thies of Monocacy Pottery with Bill vanGilder - here is the link - very interesting -
    and they sell the plans on how to build it. Hopefully I can take a trip to visit him before I build it and learn in person how to fire it. This is one of my (many) dreams anyway.

  7. Linda you are so right about the cost of fuel - and the cost of building a kiln. I'll look at the web page for the manabigama kiln - sounds interesting.
    A lot of folks are adapting their reduction ^10 glazes to fire at ^6 to save costs.
    I will gladly share my ^6 ox. glazes when you start working at home. I find there are so many variables - claybody, application, mixing, kiln firing (even electric) that no one's work looks like mine even using the shared glazes. And lots of folks have shared with me.
    And I too dream of having a big studio . . . .

  8. Hi Judy, What a generous offer to share your glazes. I think we should all share our glazes as I have found the same thing as you. In our classroom sometimes we all use the same glaze and the pieces are completely different.

    That might be an interesting thing to do with the next glaze firing. Give the same vessell to three or four different people and see what comes from their all using the same glaze on the same form. I may do that if I have time.

    And I may contact you some time about your glazes. Thanks or the offer.

    Yes, the big studio ...


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