Because Brick is My Choice

Handmade bricks used to be very commonly used throughout the UK. The process involves putting the clay, water and additives into a large pit where it is all mixed together by a tempering wheel generally still powered by horse power. Once the mixture is of the correct consistency, the clay is removed and pressed into moulds by hand. To prevent the brick from sticking to the mould, the brick is coated in either sand or water. Named ‘slop moulding’ when dipped in water and ‘sand struck’ when coated in sand. Coating the brick with sand however gives an overall better finish to the brick. Once shaped, the bricks are laid outside to dry by air and sun where they will be drying for three to four days. After this process the bricks are then transferred to the kiln for burning. If green bricks are left outside for the drying process and are left out during a shower; the water leaves an indentation of the brick is considered very undesirable. However this does not affect the strength properties of the bricks. Bricks are now more generally made by large scale manufacturing processes using machinery. This is a large scale effort and produces bricks which have been burned in patent kilns. There are three different types of manufacturing process for machine made bricks - the soft mud process, the stiff mud process and the dry clay process for which machines are specifically designed.
The ‘Soft mud ‘process is similar to that of handmade bricks. In the Soft Mud process that clay contains too much water to be extruded as the clay is left to soak in water for 24 hours. For this process three pits are usually in operation at any one time to keep the production flowing. Occasionally the clay is worked in a pug mill before being thrown into the machine. Due to the 20% water content of the clay, wooden moulds are generally used and are lined with either oil or sand to stop the clay sticking. After being drawn from the machine the filled moulds are emptied by hand and the bricks taken to the dry shed. So the soft mud bricks can be dried properly, both handmade soft mud bricks and machine made (more mass produced) bricks will both be placed in a large dryer which is separate from the extrusion dryer.
The ‘Stiff mud’ process differs because only enough water to create plasticity is added to the clay, approximately 12% water. Clay is then extruded through a ‘die’ to produce a long stream of pressed clay which is then cut to size by the machine. The die sizes and cutter wire are calculated to compensate for the shrinkage of the brick during drying and firing. Attachments can also be added to the die which gives the brick its texture from brush, roll, and scratch to roughen. Green bricks are then dried out carefully to ensure a consistent colour and strength. Because Soft Mud bricks have been created under little or no pressure, their density is not as great as that of Stiff Mud bricks. It has been argued that when Soft Mud bricks have been made and burned properly they are possibly the most durable brick. However Stiff mud bricks can have defects or planes of separation which can affect the bricks durability. However as Stiff Mud bricks are becoming increasingly cheaper to produce these are becoming the more popular.
The ‘Repressing’ of a brick is to re-shape the brick or round of any corners dependent on specification. Both types of soft mud and stiff mud bricks can be repressed when they are only partially dried. This is done by placing the bricks in metal moulds and putting them under great pressure before burning. Pressed bricks however are machine moulded bricks where the clay being used is already nearly dry. This process can make a significant difference on the appearance of the bricks. Bricks made using this process generally are more difficult to compress. Dry pressed bricks however are now commonly used for face bricks. Pressed bricks generally mean dry pressed bricks, but many face bricks are made by repressing soft mud bricks.
‘Cement’ bricks made from Portland cement, these bricks are machine moulded into size and shape to match the size of clay bricks. These are extensively used in some regions.
‘Hollow, Terracotta or Tile’. This type of product can made into practically and size or shape for any kind of use. Blocks made of terra-cotta are light and durable. For use in partitions the terra-cotta is mixed with sawdust which burns off in the kiln, but creates a more porous brick. Terra-cotta can be glazed or unglazed.
Facing Bricks Types of:-
Facing bricks are uniform in colour and shape and can now be made to any almost any specification, texture, colour and size.
Wirecut extruded bricks. For this type of brick the clay is extruded and cut by wore into individual bricks. This is a very cost effective way of producing bricks and is done by an automated production process. These bricks are readily available in a variety of styles and colours.
Stock bricks; are usually slightly more expensive than wirecut Bricks. These are a soft mud brick which are sometimes irregular in shape.
Handmade bricks; as previously discussed above, handmade bricks are very desirable and individual in shape and colour. This brick is one of the most expensive sorts of brick.
Fletton or London Brick; is a brick made from clay extracted from the south east of England which contains traces of oil which is burnt off during the burning process in the kiln.
Arch and Clinker bricks This term is used for bricks which are burned immediately. They are over burnt and sometimes distorted in shape. Body, Cherry and/or hard bricks. These bricks are of a higher quality and are generally the bricks that were in the centre of the pile of bricks which have been burned. These bricks are top bricks as they have a higher overall quality and finish. Cherry is used as a term when the clay which has been used burns red.
Salmon, Pale or Soft bricks. These are the bricks which were nearer to the outside of the kiln during burning which means they are slightly under burnt. These bricks are generally softer than the bricks taken from the centre of the kiln are therefore are of a lesser quality, although this does not affect the overall shape of the brick. These bricks are generally used for the interior of walls.
Waterstruck Brick This type of brick is a soft mud moulded brick. It uses alluvial clay which deposited at the end of the last ice age. The clay is pressed into mould lined with silicate. When the bricks are removed from their mould, they are left with a textured effect which can only be achieved using this method. This type of brick looks old and handmade even when new.
Engineering Bricks Engineering bricks are called so due to their overall strength and water absorption. The Class A brick has strength of 125N/mm² and water absorption of less than 4.5%. Class B engineering bricks have a strength greater than 75N/mm² and water absorption of less than 7%. Traditionally used in civil engineering, these bricks are also useful for damp courses and structural design.
Bullnose Bricks These special bricks are used when round edges are needed, for gate recesses, quadrants or arches.
Off Shades or Seconds or ATR or Random Quality. These are batches of bricks which are generally consistent in colour but do not match the product which is marketed.