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Chris Clyburn

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Posts posted by Chris Clyburn


  1. I would also add a caution:

     

    Take a few ceramics classes before diving into building a kiln, and everything else.

     

    Get a feel for it, and some hands on knowledge, especially of firing and how ceramic materials work. It is a very fun and rewarding field of study, (though not always financially rewarding unless you have a good head for business...as important or more so than being good at art). It is also very technically and physically challenging, especially when you are talking about architectural ceramics and large scale works. Start small and build a good foundation first, and you will thank yourself later :-)


  2. Thanks for your helpful insights, Chris. I'm very process-oriented but ignorant regarding these technical issues. Can you (or anyone here) suggest an online primer or book I can consult in order to bring myself up to speed? Thanks for confirming the superior strength of vitrified stoneware vs. earthenware, especially when unglazed.

    I'll have to look around and see what's out there online.

    Some good books however are:

    Daniel Rhodes: Clay and Glazes for the potter

    Frank and Janet Hamer: The Potter's Dictionary of Materials and Techniques

    Joe Finch: Kiln Construction: A brick By Brick Approach

    Frederick Olsen: The Kiln Book

    Emmanuel Cooper: 10,000 years of pottery

     

    You caught me in the middle of a move, so all of my library is currently packed, this is just what I could remember, I know I'm forgetting some big ones here, but I can't think ...packing on the brain :-)

     

     

    It sounds like stoneware at cone 6 might be optimal for me: suitable strength and durability at minimal temperature, with minimal fuel costs and (maybe) reduced kiln construction costs. I understand the gist, but would appreciate a clarification:

     

    Q1. What does this mean, "...at a firing rate of 108F per hour during the final ramp"?

     

    I think it describes a carefully monitored temperature change, but I don't understand the specifics. Clearly I need to study up, but appreciate any elaboration in the meantime.

     

    This refers to the firing schedule used. Vitrification of ceramic ware is measured through the use of pyrometric cones (a combination of clay and glaze) that soften and bend at at precise points based on heatwork (a combination of time and temperature) Firings usually occur in stages also known as ramps. For instance a 4 ramp firing would be 100 F /hr to 200 F and hold the temp for 1 hour (or longer this is known as candling and helps dry out any remaining moisture in the clay). Then you'd be on the second ramp say 80 F/hr to 1100 THe third ramp would be 350 F to 1638F with the final ramp being 108 F to 1888. This final ramp is where the main measurement of heatwork occurs.

     

    There are reasons for each stage. The first stage or ramp is just below the boiling temperature of water and drives of any remaining moisture without risk of steam expolsions. The second ramp is to burn of any remaining organics and allow any gas to escape, this is done slowly to ensure that there will be now little to no outgassing that will occur during the glaze firing which would cause defects in the glaze such as pitting. The third ramp is to get you to the last 250 Degrees below the final temp at which point it is fired at the rate needed to reach the final maturation temp with the proper amount of heatwork applied. I hope that clears it up.

     

     

     

    Again I did not understand the significance of these issues. I thought a broad firing range was a 'pure benefit' because I didn't realize strength and color would vary based on firing temps within that range.... Duh.

     

    Q2. So is this right? I need a STONEWARE CLAY BODY with a narrow firing range, that vitrifies nearly white at cone 6 or lower.

     

    If I cannot find something that fires nearly WHITE, I could substitute two options instead: a gray (cool) and a buff/tan (warm).

    Precisely

     

     

     

    This kind of advice from someone who knows is most helpful. I'm "100% theoretical" at this point and I understand what a handicap that is.

     

    Q3. I've read that in some cases bone dry paper clay can be glazed and fired in a single firing. Is that accurate? Are there special considerations or conditions?

     

    Any clay can be glazed and fired in one go (known as once-fired) Things to consider are: The clay has to be bone dry, with absolutely no moisture. It should be fired relatively slowly, and you can significantly increase your risk of loss if not careful.

     

    Q4. "The cost difference between earthenware and stoneware when once fired is very little". Assuming I can single-fire my work--glazed and unglazed-- are you referring to the fuel cost specifically? Are you saying it takes just a little more fuel to fire the stoneware?

    Fuel cost specifically. It with a welll insulated kiln it does not take much more fuel to go from lowfire (below cone 1) to mid fire (cone 1-7) from low fire to hifire (up to cone 10) does use a significant amount of fuel.

  3. I'm in my Confused Early Stages, so please bear with me.

     

    MY QUESTION

    Should I choose a STONEWARE clay body such as Minnesota Clay MB STONEWARE

    or a lower-fire EARTHENWARE?

     

    BASIS FOR QUESTION:

     

    LACK OF EXPERIENCE

    I'm new to this and want to keep things as simple as possible.

     

    INTENDED WORK PRODUCT

    Tiles and larger flat forms involving relief sculpture to be affixed to interiors of buildings - as in the case of a kitchen backsplash, a fireplace surround, a segmented mural.

     

    TECHNIQUES

    Handbuild, carve, press mold and slip mold.

     

    PAPER CLAY

    I intend to use paper clay methods as much as possible.

     

    KILN CONSTRUCTION and ENERGY COST ECONOMY

    I hope to build a natural gas kiln. I want to limit energy costs and kiln construction costs as much as possible. Am I correct in thinking earthenware clays and related glazes fire at much lower temperatures than do stoneware clays. If so, perhaps I do not need a stoneware clay body... Perhaps choosing an earthenware instead will significantly reduce my firing costs and kiln construction costs(?). Any advice appreciated.

     

    STANDARD of ABUSE

    Finished product must withstand the knocks and scapes and washings that occur in any household. Imagine the abuse a doorframe suffers. In many instances, I will not employ a glaze. My work does not need to hold water (as vitirified clay can) but it will likely be washed with water and mild cleaning products occassionally - especially if a kitchen surface. Would an earthenware body stand up to houshold impact and washings, or must I opt for vitrified stoneware?

     

    WHITE

    I want as white a claybody as possible. The MB Stoneware (per link above) fires nearly white in oxidation. Is there an earthenware that will meet the "abuse standard" described above and also fire nearly white in oxidation?

     

     

    If my question is too broad, can someone please point me in the direction of an online source whereby I can educate myself further.

     

    Thanks,

    Tom

     

     

     

     

    I think you'd be better off with a more vitrified clay. The less vitrified a clay is, the more fragile it is in my experience. Stoneware would hold up much better especially unglazed, than earthenware under those conditions. Earthenware generally fires at cone 04-01 (roughly 1945 F to 2046 F at a firing rate of 108 F per hour during the final ramp) whereas a typical stoneware body fires at between cone 3 to cone 10 (roughly 2106 F to 2345 F at a firing rate of 108 F per hour during the final ramp) depending on the body, with cone 6 (roughly 2232 F at a firing rate of 108F per hour during the final ramp) being very popular right now.

     

    The clay body you listed is rated cone 6-10 which means it would not be truly vitrified until cone 10, and would not be as durable at cone 6 or as white, but it would still be stronger than earthenware. If you found a white stoneware that matured at cone 6 or lower without such a broad firing range, you would be better off something like Highwater's Little Loafer's which is cone5-6 or another similar body (it's late and that's the only white stoneware with a narrow range I could find quickly ..sorry) You might also look at Lagina's paper clays, a cone 6 porcelain or a cone 6 white sculpture clay.

     

    The cost difference between earthenware and stoneware when once fired is very little, if you bisque first it become more noticeable but not enough to offset the difference in durability in my opinion

     

     


  4. I am looking for pink and purple cone 6 glazes.

    Any help would be appreciated.

     

     

     

     

    Take a look at this article:

     

    http://www.brackers.com/special_pages/rare_earth_elements.cfm

     

    It covers using lanthanides as colorants. It includes base glazes for cones 8-9 ox, cones 5-6 ox and cones 9-11 celadon type glazes as well as the suggested proportions for each oxide. This includes a nice pink using 8% erbium and a lavender 5.5% neodymium oxide with 1% 6 Tile Kaolin.

     

    I played with these when Ceramics Monthly featured an article about them in the early 2000s and you can get some very interesting and unique effects.

     

    Erbium oxide is roughly $15 per 1/4 lb and Neodymium is roughly $10 per 1/4

     

    Most of than lanthanides can be found at Laguna distributors and I thought there was another company US Chemical or something like that (I haven't had a set up to mix my own glazes in about 5 years) that sold them, but I can't seem to remember the exact name of the company anymore, sorry.

     

     

     

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