Ceramic Raw Materials Questions and Answers

Answer: A

Correct answer: plastic and non-plastic materials

The division is functional rather than descriptive: plastic materials, the clays, give the body the workability it needs to be formed, and non-plastic materials - fluxes and fillers - control what happens to it in the kiln. Every body is a compromise between the two, because plasticity is also what causes shrinkage.

Answer: B

Correct answer: clay, feldspar and quartz

The three points of the triangle are the three functions: clay for plasticity and for the mullite it forms on firing, feldspar as the flux that produces the glassy phase, and quartz as the filler that opens the body and limits shrinkage. Porcelain, vitreous china and earthenware differ chiefly in the proportions of these three.

Answer: C

Both are true and the reason gives the durability of the scheme: a body must be formable, must vitrify at an achievable temperature and must not distort, and these three materials answer all three requirements economically.

Answer: D

Correct answer: act as a filler controlling shrinkage and distortion

Quartz is the non-plastic skeleton. It reduces the total shrinkage because it does not shrink itself, opens the body so that drying and firing gases can escape, and gives the piece enough rigidity at temperature to resist sagging. What it does not do is contribute plasticity, colour or fluxing.

Answer: A

It melts at a moderate temperature and dissolves some of the surrounding material, producing the glass that bonds the fired body. Without a flux the body would need a far higher firing temperature to reach any strength.

Answer: B

The first two are correct. The third confuses quartz with feldspar, since quartz is the refractory filler and remains largely unmelted while the feldspar provides the glass. The distinction between filler and flux is the whole basis of the triaxial scheme.

Answer: C

Correct answer: False

Quartz melts at over 1,700 degrees, far above any whiteware firing, so it remains as discrete grains in the fired body. The glassy phase comes from the feldspar, which melts incongruently in the region of 1,150 degrees. A little quartz does dissolve at the edges of the grains into that melt, but the bulk of it survives as quartz - which is why the 573 degree inversion still governs the cooling schedule.

Answer: D

Quartz, feldspar, alumina and grog are all non-plastic and must be carried by a plastic component or by an added binder. The term describes forming behaviour rather than any chemical property. A material can be chemically reactive and still be non-plastic.

Answer: A

Both are true and the reason gives the requirement: advanced ceramic bodies containing no clay at all rely on polymeric binders to supply exactly what clay provides naturally in a traditional body. Binder choice becomes a formulation decision in its own right.

Answer: B

Traditional bodies are built on clay, feldspar and quartz taken from the ground, while advanced ceramics use synthesised powders of controlled purity and size. The distinction is one of raw material and of tolerance rather than of age.