Jump to content

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

Recommended Posts

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.




  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.

Link to post
Share on other sites

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.

Link to post
Share on other sites

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.



Link to post
Share on other sites
  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.

Link to post
Share on other sites

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.





Link to post
Share on other sites


This topic is now archived and is closed to further replies.

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.