Page 165 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

Chapter 3 Scientific principles

Ceramics and fireclays

Ceramics and fireclays are used mainly for sanitary appliances and tiles. There
are three varieties that plumbers may use widely in their work:
1 Vitreous china: this is a clay material with an enamelled surface used to
manufacture bathroom appliances such as WCs and cisterns, wash hand
basins and bidets, as well as soap dishes and other sundry bathroom items. It
is made from very watery clay, known as ‘slip’, which is then spray enamelled
and fired in a kiln at high temperature.
2 Fireclay: this is used primarily for heavy-duty appliances, such as Belfast
sinks, London sinks, cleaners’ and butler’s sinks and shower trays, where
there is greater risk of damage and a higher water temperature may be
needed. Like other clays, this clay is highly malleable in its raw form. It can be
moulded, extruded and shaped by hand. It is also used in the manufacture of
building products such as chimney pots.
3 Ceramic tiles: these have many applications and are used extensively in
bathrooms, kitchens, floors and swimming pools. The origin of the tile can
be identified from looking at the reverse of the tile. This is known as the
‘biscuit’ of the tile. Tiles made in the UK usually have a white-coloured
biscuit, Italian tiles usually have biscuit that is cream in colour, and Turkish
and Spanish tiles have a dark red biscuit.

Principal properties of solid materials

Solid materials are made up of many molecules. How these molecules are
arranged and how they behave under certain conditions will determine their
properties. A solid material is assessed by its:

● strength – tensile, compressive and shear
● ductility
● malleability
● hardness
● conductivity – heat and electricity.

Tensile strength

Broadly speaking, the tensile strength of a material is a measure of how
well or badly it reacts to being pulled or stretched until it breaks. Some Tensional stress
materials, such as plastics, will stretch or elongate before breaking; others, p Figure 3.1 Tensile strength
such as metals, will also deform in a similar way but not by as much, and
hard materials such as concrete and brick will not deform at all but will IMPROVE
simply snap. YOUR MATHS

A tensile strength test is also known as a tension test and is the most Tensile strength is
fundamental type of mechanical test that can be performed on a material. measured in units of force
The tests are simple and relatively inexpensive. By simply pulling on a material per unit area. In the SI
under specific conditions, how the material will react to being pulled apart will system, the unit is newton
quickly become apparent. The point at which the material fractures is its tensile per square metre (N/m²
or Pa – pascal).
strength.

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