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| © Eugene Brennan |
"Plastic" is a term applied to any material that can be moulded or bent into shape; for instance, soft toffee, modelling clay, or red-hot iron is plastic because it can be reshaped. In general though, when we speak of plastic, we mean polymers or synthetic materials made from petrochemicals.
They began as steam or drop hammers, first used in the 1840s for forging large components or driving piles. Steam was used to raise the hammer which was then dropped. Hydraulic presses take a more gentle and less noisy approach, slowly squeezing white hot pieces of steel which can be massive. They also put less stress on the material being forged, shaping it uniformly and reducing the likelihood of flaws. Steam hammers are still used for pile driving.