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38 Cards in this Set
- Front
- Back
What is the purpose of flux in glazes?
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Flux allows glassformers to melt, and influences surface texture and color.
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What are some glassformers listed as ingredients in our glazes?
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Silica (Si02/Flint) and Boron as bases, Arsenic and Phosphorus as additives.
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What is used as a stabilizer in our glazes?
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Alumina (Al2 03)
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What does a stabilizer do in a glaze?
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Stabilizers affect the mixture's viscosity.
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What is viscosity?
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The tendency of a liquid to resist flow.
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What are some fluxes found in glazes?
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Feldspar, Fritt, Talc (Mg CO3), Whiting (C2 C03), Dolomite (Mg Ca CO3), Wolastonite (C2 Si O2)
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Fritt does what as a flux?
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Fritt makes ingredients less soluble and makes toxic materials like lead safer to use.
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Talc, Whiting, Dolomite, and Wolastonite contain natural fluxes, such as?
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sodium, potassium, calcium, magnesium, barium, lithium, zinc, strontium, lead
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Some colorants in glazes are...
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iron (many colors, brown), chrome (green), copper (green), cobalt (blue), manganese (grey-brown), nickel (grey-brown), vanadium (yellow),uranium
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What are some influences on the color of glazes?
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percentage of colorant to other ingredients, atmosphere in the kiln, temperature fired, flux
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What is reduction?
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a reduction in the amount of oxygen in the kiln- physically alters glaze, coloring, etc.
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What are some opacifiers and what do they do?
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Tin, zirconium, and titanium all make glazes white and opaque.
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What kind of glaze did we use on stoneware projects?
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cone 9- high temperature
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What 4 categories of ingredients make up a glaze?
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glassformer, stabilizer, flux, colorant
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What is clay made of?
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decomposed igneous rock
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What is primary source clay?
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it is found near the rock it came from, and is thus coarser and more pure.
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What is secondary source clay?
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found far from its source, this clay is broken into fine particles. has lots of impurities.
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what is the shape of a clay particle?
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clay particles are flat hexagonal shapes that slide against eachother. they are in clumps in coarser clay.
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How does clay become more plastic?
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natural agents like mold and bacteria break down clay and make it aged and plastic. water forms a slippery film between plates.
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criteria to choose clay by include...
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color, temperature required, plasticity
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pure clay is what color?
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white!
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what is the chemical formula of pure clay?
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Al2 O3 2S1 O2 2H20 (or, alumina-silica-water)
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the clay we use is made of what 3 categories of ingredients?
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Clay (duh), filler, and flux
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What are some clay types, in order of higher temps/coarser to lower temps/finer?
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Kaolin, fire clay, stoneware, call clay, earthenware, bentonite
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what are some fillers in clay?
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grog, sand, flint
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what are some fluxes in clay?
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feldspar, talc, fritt
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what is meant by "vitreous"?
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water-tight, having a hard, glassy surface
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what is meant by "refractory?"
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material that can withstand high heat, like clay!
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What is grog?
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ground up fired clay
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what do fillers do?
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adds strength, reduces shrinkage, adds hard, non-plastic particles.
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about feldspar:
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for high temps, a natural decomposed igneous rock.
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about talc:
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magnesium silicate, in earthenware
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about fritt:
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man made. carefully chosen ingredients to control necessary temperature. ground up glassy material.
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When/where/what were the earliest known glazes?
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c. 5000 BC, in Mesopotamia and Egypt- Sodash and Borax (water soluble). Egypt had a turquoise paste.
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Early firing was done in_______. What problems did this cause? why?
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pitfires. made unstable, pourous pieces, due to lack of high temp
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following pitfires, ceramicists invented an_________ system for more durable pieces
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updraft/bank
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after updraft firing came_______. when/where?
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downdraft kiln. Hunn dynasty in china, 200 BC. used wood ash, limestone, feldspar as glazes.
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about porcelain:
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kaolin, feldspar, limestone. originated in china.
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