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1951
26 July 1951
Industry Begins At Home
Smoke rises in lazy puffs from a hill overlooking Mudgee, where a brick yard stands on the bank of a quarry, and Putta Bucca Lane winds away over the skyline.
A distinct asset to many aspects of Mudgee life, this lonely cluster of brick structures and tall, gaunt roofing over massive machinery produces weekly about 20,000 bricks It is owned by Mr. Adam Roth, who finds a ready market for them, not only in Mudgee but in many other centres, near and far, where the demand is influenced by the present shortages checking the normal expansion of towns and cities.
Three long, low, domed kilns with solid brick walls run parallel, their mouths facing the quarry. Between the kilns and the quarry are the monstrous grinder, the brick machine, heaps of fuel, and a great old traction engine - a cross between a present day steam roller and a gigantic version of Emmett's famous caricatured engine.
Contrary to pre-conceived ideas on brickmaking, we discovered that the material is shale, not clay. Of course, clay is often used, but the shale apparently, makes a finer, stronger brick.
Looking down the steep sides into the quarry, you can see the shale, which is like splintered flakes of rock, white and grey with black and green streaks. The work of quarrying is now greatly reduced by the use of a bulldozer, which seems to have a very precarious hold on Mother Earth when making sorties into the deep hole for loads of the shale - like a fly on a wall; but flies are more adapted to that sort of thing.
With a winch the shale is raised and fed into the grinder, a huge bin topped by engine-driven axles and cogs in dismaying confusion.
Inside are great cogs turning, like the wheels of Time, slowly, surely, inevitably to meet and crush to powder the shale. The immensity and the very certainty of this great, slow-moving thing is enough to give a mere pumy human the shivers.
Then the greeny-grey heap of material - like sand but softer - is screened, or filtered, to remove the larger particles, and on it goes through a chute to the brickpress.
So much for the preparation; now for the actual manufacture.
The press used here is the most modern and effective type found anywhere, distinctive in its performance of the operations of pressing and drying at once. This is a far cry from the old methods of pressing, when the wet moulds had to be laid out to set and dry for some time before burning was possible.
The material goes into the press in an almost dry state. With such pressure to mould them, it is not necessary to set the bricks like a concrete mixture.
Imagination can readily form an idea of how such a press works. Driven by a 40 h.p. diesel engine, it stands about 6 feet high in a complicated construction of frame, wheels and moving parts. For the actual pressing there are upper and lower "dies," or moulds, which fill from a box which slides in and out at the completion of each brick, and come together to mould the brick. To prevent the bricks from sticking to the dies, the latter are heated by steam which is supplied through castings from the boiler of the old engine, which was once used for chaffcutting.
"Cams", wheels with the spindles set off centre so that the motion is not circular but more like that of a buckled wheel, roll to press the upper die down to meet the lower one, which is raised from beneath. Now in perfect form, the brick is released by the retracting motion of the dies and pushed out onto a plat-form by the incoming box, which slides back and forth like a truck on rails.
At this stage - an interesting discovery for the newcomer to the business - the bricks are quite green.
Novel iron handbarrows with rubber-tyred wheels (motor-cycle wheels), carry the bricks from the press, which can turn out 1200 bricks an hour, to the kiln. These three kilns are used in rotation. While one is burning, another is being emptied and the last is being filled. They are each 35 feet long by 16 feet wide, and the domes are 10 feet six inches high. With the bricks stacked like miniature bales of green lucerne hay, the kiln is closed and burning begins.
In the eight fire boxes built into the 4 feet thick walls of the kiln coal fires are burnt, the heat being gradually increased. About 50 tons of coal are burnt for each kiln of bricks.It takes two weeks to steam the bricks, the second week with a full fire, and a third week for the kiln and contents to cool. Samples are tested through a small opening in the dome for shrinkage, for a brick shrinks as it burns.
A tricky business, burning is just like baking, a whole kiln - 40,000 bricks - can be ruined by having the fires too hot at the wrong times, or by too much or insufficient burning.
You see many different coloured bricks, some cf which are more popular than others. But the interesting fact is that the only difference in the process for all is the length of time of burning, or the decreasing of heat at certain times by letting a little air in. A black brick can be produced by more burning, and it is noticed that there are often a few black ones in an ordinary kiln as the outside bricks sometimes tend to receive a little more heat from the fires, from which the heat rises in what is called an "updraft".
The admired glaze on the surface of earthen pipes and some bricks in vise is obtained quite easily by causing the surface of the brick or other mould to melt more quickly. A quick fire in which salt is burnt will achieve this.
It is rather a more specialised study, brickmaking, than is generally thought, and certainly a necessary one if we are going to have the materials for our homes1
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