Chasing the Craze: When the Right Variables Are Off-Stage Tina M

Art and Art History Faculty Publications Art and Art History 3-2016 Chasing the Craze: When the Right Variables are Off-Stage Tina M. Gebhart Gettysburg College Follow this and additional works at: https://cupola.gettysburg.edu/arthfac Part of the Ceramic Arts Commons Share feedback about the accessibility of this item. Gebhart, Tina M. "Chasing the Craze: When the Right Variables are Off-Stage." NCECA Journal (2016). 85-87. This is the publisher's version of the work. This publication appears in Gettysburg College's institutional repository by permission of the copyright owner for personal use, not for redistribution. Cupola permanent link: https://cupola.gettysburg.edu/arthfac/19 This open access article is brought to you by The uC pola: Scholarship at Gettysburg College. It has been accepted for inclusion by an authorized administrator of The uC pola. For more information, please contact [email protected]. Chasing the Craze: When the Right Variables are Off-Stage Abstract A smooth white glaze, (Figure 1) with a buttery surface and smooth breaking on edges, just enough change of whiteness in a crevice pooling, seemingly opaque when thicker, but with a certain glow, a slight grey showing through. It crazes slightly, a fine ew bbing of cracks. Not enough to be decorative crazing, and not enough crazing to make me abandon the glaze, but enough crazing that I would like it to be gone. I prefer a system- oriented testing approach as a kind of universal order. A simple Unity Molecular Formula grid mapping method typically shows a boundary line of crazed and non-crazed surfaces and trends in surface quality. Sounds simple enough. But, as has been said, there is no need to seek the ceramic troubles. They will find ouy . (excerpt) Keywords glaze, ceramic glaze, ceramics, unity forumula mapping, unity molecular forumla, universal glazing theory Disciplines Art and Design | Ceramic Arts This article is available at The uC pola: Scholarship at Gettysburg College: https://cupola.gettysburg.edu/arthfac/19 Sharp-edged cracks in the fired glaze (the crack looks like you hit it with a hammer)-these are cooling cracks that occurred after the glaze had hardened at some point in the cooling cycle. Round-edged cracks in the fired glaze (the fired glaze rolls back from the crack)- these types of cracks occur either in the forming, drying, or bisque firing stages and then the glaze is applied over the ex isting crack. At some point potters will have to diagnose and solve a de The best method for finding a substitute clay is to first deter fect caused by kilns, clays, or glazes. Be prepared w ith a little mine what group the original clay fa ll s with in . Clays are divided knowledge, which can prevent a lot of frustration. into the follow ing classifications: fireclays, stoneware clays, ball clays, kaolins, earthenware clays, and bentonites. Once you have determined what group your clay fa ll s within, choose a replace Chasing the Craze: When the Right Variables are Off-Stage ment from the same group, then fine tun e the search regarding Tina Gebhart its fired color and plasticity. Note that there are variations within each group as some kaolins are more plastic than others and some stoneware clays can fire darker than others. For example, Grolleg, In Pursuit Of The Future: a plastic kaolin, can be substituted for E.P.K. , another white firing "Removing Flaws, Maintaining Interest: plastic kaolin. Conversely, a less suitable choice would be usi ng Ceramic Glaze Improvement Methodology Gold art stoneware clay, wh ich has a lower iron content th an New via Unity Formula Mapping man Red stoneware clay. Obtaining a chemical analys is sheet on The Quest: the clays or asking your ceramics supplier can further gu ide your A smooth white glaze, (Figure 1) with a buttery surface substitution choice. and smooth breaking on edges, just enough change of white General Guidelines for Glazes ness in a crevice pooling, seemingly opaque when thicker, but with a certain glow, a slight grey showing through. It crazes Commercial or potter developed glazes are composed of sli ghtly, a fine webbing of cracks. Not enough to be decorative processed and/or raw materials. When developing glazes, al crazing, and not enough crazing to make me abandon the glaze, ways order the whole original processors bag as opposed to just but enough crazing that I would like it to be gone. getting a 5 lb. bag of white powder, which might not be what I prefer a system-oriented testing approach as a kind of you ordered. Ask for a chemical analysis sheet, which wi ll state universal order. A si mple Unity Molecular Formula grid map the particle size of the material and reorder from the same pro ping method typically shows a boundary line of crazed and cessor and the same particle size. This wi ll insure a consistent non-crazed surfaces and trends in surface quality. Sounds sim glaze result. Most raw materials used in the base glaze (exclud ple enough. But, as has been said, there is no need to seek the ing coloring oxides, additives, or stains) such as flint, feldspar, ceramic troubles. They will find you. talc, dolomite, kaolin, etc. are less expensive per/pound when ordering the whole bag. However, due to their expense, materi Glaze Theory & Approach: als such as cobalt oxide, cobalt carbonate, stains, and tin can be This series of tests hoped to become the foundation of a purchased in small amounts. larger flaw improvement system. A "Universa l Glazing Theory" Whether using commercial glazes or you r own fo rmulas, the of sorts, in in itiall y focusing on a single glaze recipe that is a most frequent defects occur when applyi ng the glaze too thin or work in progress. I share with you an inquiry process that com thick. Thin glaze applications can cause a lack of glaze color or bining discovery tactics with a systematic testing approach. reveal the underlying clay body color. Thin appli cations can also These glaze tests aim to remove crazing (fine webbing of have a rough surface due to an insufficient layer of glaze. Exces cracks in the glaze) from the Smooth Satin Matte glaze I use, sively thick applications can cause a glaze to run down vertical surfaces or pool in recessed horizontal areas. In extreme instanc es, a thick glaze can cause sharp-edge cracking in thin wall ed Smooth Satin Matte C/10 reduction forms due to clay body and glazes incompatible rates of cont rac Gillespie Borate 12 tion upon cool in g. Most glazes wil l work we ll if applied to the thickness of three or fo ur business cards stacked together. Custer feldspar 41 EPK 5 Cracks Two types of cracks can occur in glazed functional pottery Talc 15 or sculpture that will help the potter decide the possible cause Dolomite 7 of the problem and its eventual correction. Silica 20 nceca 85 Journal 2016 • Panels using a un ity formula grid surrounding the original recipe (at initial eye-based observation, it appeared that the crazing was center of grid). The g rid samples are in unity formula incre alleviated in the step to the right of the original sample. In at ments of 0.5 Si02 across the X axis and increments of 0.05 least one of the preliminary puck grids, the crazing was visu Al203 up the Y axis. ally alleviated in a region, and in later grids, crazing was visu ally eliminated in large regions. Unity Molecular Formula • KNa20: 0. 21 • Si02: 2.984 Testing Process: We used test pucks desig ned to be simple yet show certain · total glass former (Si02 + B203): 3.11 form details that I use in my pots. The round, flat tiles with ap • CaO: 0.325 • Alumina : 0.266 plied groves show both breaking and pooling of gla ze and were • MgO: 0.461 produced mostly by research assistant Madison Seneney. After the first test firing, we fo und that on the flat puck Fashioned after the Stull & Howat1 g laze testing a cen surfaces, the crazing did not reli ably occur (or it did not as ob tury ago, the trends of other flux combinations usi ng this same viously occur). It was more pronounced (o r was more notice approach were examined by Brian Quinlan 2 in hi s research able) on the real curves of pots with the original g laze. We with Dr. William Carty at Alfred University. The resulting designed a small cup with a cut foot and in the spirit of my pots maps show changes in crazing and surface quality (gloss for two ends - to see if there was a different effect on craz satin-matte). These UMF series showed a di stinct boundary ing between the flat and cu rved surfaces, and to begin to see line between crazed and not crazed glaze increment samples, the aesthetic of the glaze in-situ fo r broader quality judgments. among other trends. Others have been inspired by this testing There was a crazing difference between these, though it may foundational approach where with a g iven flu x combinati on, be an indirect cause. increments of increasing sil ica and alumina are tested (molar). My research assistant Meagan Lupolt produced these min Essentially, we used this mapping approach but with the iature pots as dual technical training, and did so with excell ent specific Au x combination of the Smooth Satin Matte glaze, fit finesse and with increasingly skillful speed.

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