|
|
|
|
If you still have questions after checking our website please e-mail us. 最新のＡＢＣニュースはこちらへ。 最新のニュース 只今準備中。 Brick Raw Materials Generally speaking, fired clay bricks are made from no more than naturally occurring clays and shales. In most instances, the choice of a particular clay and shale will be the major factor in determining the colour of the final product. Some brick colours are achieved through the addition of other minerals to the base clay. For example, coal is often used to achieve a dark grey to almost black colour, and mangenese will give a grey brick. In some cases, a chemical slurry is applied to the brick after forming and before firing, to give a unique colour that cannot otherwise be achieved. Firing Bricks Clay bricks have been around for thousands of years of course, and for much of that time they were simply fired by leaving them in the sun. A very small number of bricks are still made this way, but certainly not commercially; some local authorities in rural Australia will allow homes to be made from mud bricks, formed in timber boxes from the clay at the site and fired in the sun. But not too many people have the time or patience to build a home this way, just a few bricks at a time! Bricks today are fired in a kiln at temperatures ranging from around 800° to 1300° Celsius. There are many different types of kilns for brickmaking, from the old style and very simple brick structure which is set by hand and then sealed at the ends with bricks and mud, to very modern computerised roller kilns and tunnel kilns. The temperature at which a brick is fired, and the duration of the firing, will have a significant influence on the colour. Also significant is the position of the brick in the kiln, because the temperature is not always going to be consistent. It is these subtle variations that come about through the processes of brickmaking that give fired clay bricks their character. Different Types of Bricks There are many different labels given to bricks, most of them derived from how the brick is made. The most striking distinction is that between extruded bricks and pressed bricks. An extruded brick is made by forcing a continuous column of clay through a mould and cutting the column into individual bricks one section at a time with a series of wires. The layperson will generally refer to extruded bricks as "bricks with holes in them". The holes in extruded bricks are created by the design of the mould and allow mortar to lock the bricks together when they are laid. Some extruded bricks are also referred to as wirecut bricks. All extruded bricks are wirecut, but the term is generally applied to those bricks with the rough textured face that is created by the wire dragging across the clay. Pressed bricks are made individually in mould boxes. Instead of having holes through them, bonding with the mortar in the finished wall is achieved by the frog, the indentation in the top of a pressed brick. Pressed bricks have been manufactured in Australia since the early 19th century when the first brick presses were shipped from England. There was a time, until perhaps twenty or thirty years ago, when a pressed brick plant could be found in most large country towns. Pressed bricks are a premium product renowned for their strength, character and individuality, but they are also slow and expensive to make, particularly in the old country brickworks that were scattered across Australia. The small rural brickmaker producing perhaps a few thousand pressed bricks a year has not been able to compete with the efficiency and huge output of the major city brick manufacturers, using modern automated extruders and kilns and producing millions of bricks in a single run. Most have gone, and pressed bricks are becoming increasingly difficult to find, and ever more expensive. The first bricks made in Australia were sandstock bricks. Soft clays were literally thrown into a timber box (the stock) which had sand sprinkled in it to prevent the clay sticking to the box. The resulting brick, sun-dried of course, had its own unique combination of lumps and folds, with a rough sandy texture. Today, these bricks are manufactured commercially by a number of Australian brickmakers, including Nubrik, PGH ("the Hand Made Sandstocks") and Austral (the "Governors"). Brick Dimensions The standard size of clay bricks varies from country to country. In Australia, the standard size is 76mm high X 230mm long X 110mm wide. This is the metric equivalent of what was the imperial standard brick size for many decades until the 1970's - 3" X 9" X 4". Because of the natural raw materials that bricks are made from, and the nature of the firing process, bricks will always vary a little in size. In Australia, the official standard for brick dimensions is applied not to any individual brick, but to twenty bricks, placed end to end, side by side or on top of each other. For example, twenty bricks placed end to end will be within the Australian Standard if they measure 4,600mm ± 60mm. Click here to see the websites of some of Australia's brick manufacturers.
|
|
Please e-mail webmaster@ale.com.au with any comments.
We do appreciate your feedback.
|
|