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Pottery Knowledge Quiz Of The Week (Pkqw): Week 8

Earthenware glazes shelves

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#1 Pres

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Posted 16 May 2017 - 01:25 PM

Week 8

New quiz folks, another hodge podge of thought raising questions.

 

  1. All of the Earthenware clay bodies can be lumped into 3 arbitrary groups:

      1. pure earthenware, talc, and kaolin bodies

      2. fritted, grogged, and kaolin bodies

      3. pure earthenware, fritted, and talc bodies

      4. pure earthenware, kaolin, and fritted bodies

  2. As temperature decreases, flux increases, and ________________ decreases.

      1. Feldspar

      2. kaolin

      3. ball clay

      4. quartz

  3. The thinnest, and lightest of kiln shelves are made of a ____________________composition.

      1. high alumina

      2. cordierite

      3. nitride bonded

      4. silicon carbide

  4. ____________ glazes are used in a lot of studios to avoid throwing small bits of glazes down the drain

      1. Trash

      2. Raw

      3. Commercial

      4. Ash

 

 

This weeks questions come from text in Electric Studio: Making and Firing, edited by Bill Jones, c. 2016, The American Ceramic Society

Note from Pres: This is one of the newer books(paperback) in my library. If for nothing else, it has a large area on the use of , repair and firing of electric kilns. This includes sections on kiln furniture, repair and upkeep.

 

 

Answers:

  1. c) pure earthenware, fritted, and talc bodies Pure earthenware clay-as mined it can contain varying amounts of flux and other impurities and it fires to whatever temperature its contaminants (sodium, potassium, iron, etc.) dictate. Fritted bodies think of it as porcelain (25 kaolin, 25 ball clay, 50 non-plastics) but with much of the non-plastics being frit and the frit often containing boron. Two subsets exist; one with lots of nepheline syenite as a flux source, another with whiting (calcium carbonate), which is problematic because its firing range is narrow. There are, of course, an infinite range of mixes of frits, feldspar, and nepheline syenite in this group. Talc bodies-similar to porcelain but they have use talc (magnesium aluminum silicate mineral) as the principal flux. Again, talc, frit, nepheline syenite, and feldspar are mixed in infinite variety to make low-fire clay bodies. The clearest example is 50 talc and 50 ball clay. Talc bodies have very little silicate glass, in fact they have very little silica and consequently they can be terribly weak better for figurines than for functional ware.

  2. (d) Quartz As firing temperature decreases, flux increases and quartz decreases. Natural Earthenware clay, as mined, contains all the sodium, potassium, iron and other fluxes necessary to fire to maturity without added materials.

  3. c) nitride bonded    From an image caption. . . . The relative thickness of three 18x24-inch kiln shelves composed of different materials. The thickest(left), a 1-inch cordierite/high alumina shelf weighing 21 pounds; the next is a thinner but denser 3/4:-inch silicon carbide shelf that weighing 20 pounds; and the thinnest shelf, a 3/16-inch silicon carbide nitride bonded shelf weighing only 9 1/2 pounds!

  4. (a) Trash It’s a fairly common practice in large studios to make what’s called a “trash glaze” using the remaining bits of various shop glazes to avoid throwing glaze materials down the drain.


Edited by Pres, 24 May 2017 - 09:27 AM.
Misspelling due to cut and paste . . .sorry

Simply retired teacher, not dead, living the dream. on and on and. . . . on. . . . http://picworkspottery.blogspot.com/

#2 LeeU

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Posted 16 May 2017 - 02:22 PM

There is a nice excerpt from this book online-it can be downloaded as a pfd:

 

http://cad-website-i...t_Revised_2.pdf

 

I ahd to look up all fo the answers so I'm not doing the quiz (brain not cooperating, at lesat at the moment.).


Lee Ustinich

 

 

 

 

 

#3 Pres

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Posted 16 May 2017 - 05:19 PM

Thanks for posting the link Lee, at least everyone will get one question correct! :huh:

 

Hate it when I have a brain freeze, I've been waiting for mine to thaw out since 1967!

 

 

best,

Pres


Simply retired teacher, not dead, living the dream. on and on and. . . . on. . . . http://picworkspottery.blogspot.com/

#4 High Bridge Pottery

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Posted 16 May 2017 - 05:51 PM

I am going for three, talc and frit earthernware seems to make sense along with pure. Kaolin is refractory. Maybe I am too pedantic but question 2 it depends what you are trying to achieve  ;) Not sure on question 3 but I do know cordierite are the heavy ones, probably SiC. Trash is the only answer that works for saving glaze.


One physical test is worth a thousand expert opinions.

 

gallery_23281_871_611.png gallery_23281_871_239.png gallery_23281_871_701.jpg

 
 


#5 jrgpots

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Posted 16 May 2017 - 10:17 PM

1. 3
2. 4
3. 3
4. 1

#6 Mark C.

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Posted 17 May 2017 - 01:00 AM

3

4

3

1

I'm hoping for the decoder ring this week


Mark Cortright
www.liscomhillpottery.com

#7 glazenerd

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Posted 17 May 2017 - 06:49 AM

1 is 3.... Kaolin is a hi temp clay.
2 is 3 or 4--formulation question. Silica levels do not drop regardless the temp, if vitrification is the goal. If not, can break any rule you want. Not enough info to answer- see below.
3 is 3... Mark owns many, he would know.
4 is 1... Better known as thermal decomposition of waste by products.

2 could be a multiple choice answer. If a fritted body is used, then silica is sourced from that instead of additions. Earthen ware can be low to mid fire, so that is a question as well.

Nerd

#8 Mark C.

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Posted 17 May 2017 - 05:43 PM

  1. Nitride bonded shelves stay perfectly flat up to 2600 degrees-they are made in electric arc furnace in a nitrogen atmosphere without oxygen present.This is an expensive process with only a few locations on this continent that do this .These are the only shelves I use in my two reduction kilns.Glaze does not stick to them.They are more fragile and you have to be careful not to thermo shock them or let them get wet as they can explode if wet and heated to fast.I have piles of other types of shelves-that are all lesser shelves.I use about 50 of them currently 12x 24s.


Mark Cortright
www.liscomhillpottery.com

#9 Marcia Selsor

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Posted 18 May 2017 - 05:47 AM

A little late at this. Been unpacking studio and house and selling the Tx house.
1-3
2-4
3-3
4-1
Marcia Selsor, Professor Emerita,Montana State University-Billings
[http://www.marciaselsorstudio.com

#10 Pres

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Posted 18 May 2017 - 07:54 AM

18 X 24 X 1" shelf in cordierite is 21#, a silicon carbide 3/4" is 20#, and a 3/16" bonded nitide is 9.5#!

 

Weigh the price against the advantages, and make decisions on your own. Mark has spoken with his choices.

 

 

best,

Pres


Simply retired teacher, not dead, living the dream. on and on and. . . . on. . . . http://picworkspottery.blogspot.com/

#11 S. Dean

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Posted 22 May 2017 - 05:01 AM

1. 3

2. 4

3. 3

4. 1







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