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ABOUT BRICK

HOW IS BRICK MADE?

Clay is extracted from the earth, with brick properties changing depending on the geographical location of the clay source as well as the depth of the clay within the quarry itself.

Depending on the required properties of the finished material it is sometimes necessary to mix clays from different locations and depths. The clay is then transformed into a plastic mouldable material by grinding and mixing with water. If there are large lumps of clay, rock crushing may be required to reduce the size of the clay rock particles.

A brick’s shape is formed by one of two processes:
Extrusion – a long clay column or slug shape is created and then cut into individual brick units. The bricks made through this method are typically perforated and may be solid but without frogs (a frog is an indentation in one or more of the bed surfaces of the brick).

Soft mud moulding – bricks are formed by mould boxes, this process can either be done by hand by craftsman who produce one brick at a time, or by automation where large numbers of bricks can be produced at one time. Bricks using this method are typically made with frogs although some can be solid.

Bricks must then be dried to reduce as much moisture as possible to prevent bursting when they are fired. Dryers are typically kept at temperatures of 80 – 120 ˚ Celsius with high humidity to keep the outside of the brick as moist as possible, while allowing the brick to dry from the inside out. Drying can take between 18 to 40 hours for standard shapes whilst specials can take longer. Green bricks, or unfired bricks, are not weather proof and can be used for internal walls or where they will be unaffected by the elements.

Firing temperatures differ between clay types. During the firing process clay particles and impurities are fused together producing a hard weatherproof material. Bricks shrink during drying and firing and this has to be taken into account when deciding on the mould size. Temperatures vary depending on the type of clay being used but typically range from 900 – 1200˚ Celsius.

Due to the very high temperatures involved the firing process takes place over three stages:
Pre-heating – this stage ensures the bricks are completely dry
Firing – fuel is then used to increase and maintain the temperature
Cooling – air is drawn into the kiln to reduce temperatures to enable the bricks to be handled for sorting and packing.

COLOURS, MORTAR, PROFILES, LAYING PATTERNS

There is a wide range of colours available in UK bricks, and with differing mortar colours and textures and laying patterns the finished looks are endless.

» See various mortar joint profiles
» Visit our members’ sites to view their available bricks