Glazing and Decoration Questions and Answers

Answer: A

Correct answer: fired on afterwards at a lower temperature

Onglaze or enamel decoration is applied to the already fired glaze surface and fixed in a third firing at 700 to 900 degrees. Underglaze is applied to the biscuit before glazing and is then covered and fired with the glaze at full temperature. The difference in firing temperature is what accounts for everything else about the two - as the next item sets out.

Answer: B

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason accounts for both halves. The lower firing temperature lets pigments survive that would burn out or dissolve at glaze temperature, which is why onglaze offers reds, pinks and bright yellows underglaze cannot. But the decoration sits on the glaze rather than sealed beneath it, so it is exposed to cutlery, abrasion and dishwashing and wears away in time.

Answer: C

The first two are correct. The third is wrong, since underglaze goes on before the glaze and onglaze after the glost firing, which is precisely what gives each its character. The stage of application determines almost everything about the result.

Answer: D

Correct answer: False

The choice has real practical consequences. Underglaze is sealed beneath the glass, so it is permanent, dishwasher-proof and safe against any release into food. Onglaze wears, and where the pigments contain lead or cadmium there is a release question the underglaze route does not raise. Durability and food safety therefore constrain the choice before appearance is considered.

Answer: A

Dipping suits hollow ware and spraying suits flat or complex shapes, and both give an even layer at production rates. Hand brushing survives in studio work but is far too slow for a factory. Application method follows the shape and the production rate wanted.

Answer: B

Correct answer: the specific gravity of the slop and the dwell time

Thickness is set at application: the specific gravity of the suspension controls how much solid is in it, and the dwell time controls how long the porous biscuit draws water and deposits solids from it. Both are measured and controlled routinely, since thickness affects colour, opacity and the tendency to craze or crawl.

Answer: C

A thinner slop carries less solid per unit volume absorbed, so the deposited weight falls. Specific gravity is checked frequently in production for exactly this reason. A drifting slop shows up as uneven glaze thickness across a run.

Answer: D

Water evaporates and solids settle, so the slop drifts if it is left alone. A hydrometer check and an adjustment are among the most routine tasks in a glazing shop. Water is added back and the slop stirred to restore the target.

Answer: A

Correct answer: contains fine crystals that scatter reflected light

A matt glaze crystallises during cooling, and the small crystals at the surface scatter the light that a glossy glaze would reflect specularly. It is a deliberate result, obtained by composition - high alumina, or magnesia, calcium or zinc - and by controlled slow cooling, since fast cooling suppresses the crystallisation and leaves the same glaze glossy.

Answer: B

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the distinction. A true matt glaze is dull because it has crystallised; an underfired glossy glaze is dull because it never melted properly and its surface is rough and pitted. They look similar and are quite different faults - the second is corrected by firing higher or longer, and treating it as a matt glaze would leave the ware porous and unsatisfactory.