Metal Casting Technologies : MCT-JUNE-2014
28 www.metals.rala.com.au / metalsonline.rala.com.au Effect of the development of Metals ne’s curiosity (not to say interest) is aroused concerning the manner in which man discovered the existence of metal – its presence in combined form in the rocks and stones of the earth, and the vital matter of recovering the metal therefrom. The first question that comes to one’s mind is whether the discovery of metal had its origin in one locality only and spread from this center throughout the world, or whether the opposite was true ― namely, that it was discovered by man in a number of localities and radiating from them covered all the then known world. It would seem more reasonable to suppose that more than one man was attracted by the two metals that could be found by observation of stream beds and fractured rocks; namely gold and copper, the latter being by far the most common and the brighter in luster. Several hypotheses have been put forward and it is not unlikely that each of them may be correct for different world localities at somewhat different times. At this point a bypath presents itself which leads away from the mundane subject of metal to the ever appealing reaction of young men and maidens in the springtime of the earth. It may happen that a certain young man was wandering along the streams of his habitat in search of beautiful things to add to the necklace for his lady love. We know that much earlier than this necklaces were the chief, if not the only, adornment for females. Clear and colored quartz with natural holes had been strung together; shells also were used for the same purpose. Of course the thing was to find something new either in color or substance to incorporate into the tribute to be presented. Our young man may easily have come across some flakes or nuggets of the attractive yellow metal, gold. When he found that this new material could easily be hammered into suitable shapes and pierced readily with the flint tools he had available, he added this find to the necklace. However, gold was hard to come by even at that period, so its use was confined in this early date to articles of artistic application. Even if a large piece was found, enough to make, say, a dagger blade or hammer, the extreme softness made it much inferior to the already available flint tools. Nevertheless, the prospecting idea would have taken root and this same young man might easily have acquired the urge to search diligently in the rocks and streams for other unusual and attractive “stones.” In the course of such a search and in one or more of several localities our newly-fledged prospector might have found pieces of reddish material that could be easily hammered and were capable of a pleasing finish. Such material was at once added to the necklace and the first use of copper had occurred. Actually native copper has been found in many places – Siberia, Brazil, Cornwall (England), South Australia and, as already mentioned, in limited areas of the United States and Canada; it is associated with the ores of copper. So far we must suppose that the use of fire to change the state or condition of a substance from a solid to a liquid had not been applied except in the case of ice. The heating of flints only served to crack them into smaller pieces and the fuel from which the fire had been made had, for the most part, disappeared into thin air leaving only a dry, useless material. And now another lane of interest appears in our wanderings which lead to that ancient institution, the “camp fire.” Its purpose was to warm those who were building it, or to keep at bay wild animals, or to cook the elementary meal by roasting meat transfixed on a wooden skewer, or possibly to soften some grain, the product of the incipient agriculture of that early day, in the pottery vessels then available. It is reasonable to consider that as time progressed the fire was circled by stones and attention given to raising the wood above the ground in order that air might more readily have access, thereby greatly increasing the temperature obtained. In the wanderings of these people from place to place one may imagine that they found themselves in a district in which copper ores abounded and, quite unconsciously, used pieces of the ore to fence in their fire. Imagine the interest that would be created when little rivulets of red-hot liquid were seen to be trickling away from the hot part of the fire, and how the changing of this bright red liquid to a dark brown solid would be watched by the more inquisitive member of the group. The next morning this same inquirer would hasten to the ashes and unearth the dark brown ribbons. He would find that he could bend them but that after a few turns the ribbon broke, exposing a salmon-pink colored substance with numerous holes distributed therein. By this time the campers had to move on, and reluctantly, the inquisitive member had to leave with O Back to the cast Bronze – its origin, use and influence - Part 2 Prof. John H. D. Bautista, PEE, RMetE, MBA; Technical consultant, Phil. Metalcasting Assn., inc. METAL casting Technologies June 2014 29 them, but not without looking forward to the next camp fire to continue his investigation. Alas, that night no copper ore was used to fence the fire and in vain was search made for the substance that became liquid like water and then solid like ice, but which unlike the ice did not become liquid again at ordinary temperatures. Two possibilities now present themselves, either the group moved on from spot to spot until by chance they again reached a copper locality where the process repeated itself, or our inquiring member retraced his steps to find the old location and by careful observation found certain characteristics in the stones used that differentiated them from the others. From that moment our friend became a prospector, looking for stones that, when properly treated, made what we now call the metal copper. Peake, in his book “The Bronze Age and the Celtic World,” quotes a theory held by Elliott Smith, that copper was discovered in Egypt in the following manner: The green copper ore malachite (copper carbonate) was used by the beauty parlors of that time as an eye application. To prepare it, it was ground by pounding and rubbing on a slate plate. It is supposed that, the day being cool, a dung fire was burning beside the operator, and further that some lumps of the malachite did not break down easily so in disgust the man threw them into the fire, to discover later that the little lumps of dark brown material were mixed with the ashes which, on hammering, proved to be malleable like gold but which had other properties not previously encountered. Peake, himself, questioned whether a dung fire would give enough heat to recover copper from malachite ore, but, he states, “A friend of mine, R. H. Marshall of Cambridge, demonstrated that such a dung fire was ample for the purpose.” By whatever of these or other means copper was obtained, it still remained to reconvert the solid metal into the liquid and in the doing of it to secure larger aggregates of the red metal. We should not lightly pass over this new-found ability of man to turn a solid material into a liquid and then, as a natural corollary, to produce from the liquid solids of predetermined size and shape, by running it into a suitable sand or stone molds. This was elementary melting and casting inaugurated. Another advance was made when it was found that not only was the new material copper, unlike flint, capable of being hammered into any desired shape, but that this hammering increased the hardness of the material. Even after hammering, however, the edge obtained was not equal to that of the flint tools. Probably some of the dandies of that day would wear the new copper daggers at their waistbands but the poorer classes to whom utility was of more moment than beauty continued to use the flint knife and dagger. Another trouble associated with this metal, copper, was the difficulty in its casting. Its great proclivity to absorb gases and produce a veritable sponge confined its use to open molds – even then many tools so cast had to be rejected. Evidence of such scrap castings has been unearthed in “founder’s boards” in various places. Fortunately, man was soon to find, not so much a new metal as a combination of copper and another substance that greatly improved its useful properties. In Cornwall, England, there is a tin ore carrying cassiterite (tin oxide), copper pyrites, wolframite, and quartz; this is in the Tincroft lode of the South Crofty mine. In China, and we may presume elsewhere also, copper ore and tin ore may be found in association. If the camp fire, already referred to in this article, happened to be fenced in with such a combination, the globules or ribbons of liquid coming from the fire would be, after solidifying, found to have properties that were different from those previously associated with copper. This metal, on re-melting, could be cast in closed molds and have a greater hardness as-cast and could still be hammered out to any desired shape. Once this “improved copper” had appeared, the prospector searched for the kind of “stone” that produced it. Although man came out of the Neolithic age when he started to use copper, yet the limitations of the metal were such, and the comparative speed with which it was superseded by the superior alloy called “bronze,” that it did not justify labeling the intervening period as the “copper age.” So now we have arrived at the subject of this discussion, namely the Bronze Age, in the next article. n References: (a) Harold J. Roast, cast Bronze (b) c. Drury and e. Fortnum, Bronze (c) William Alexander and Arthur street, Metals in the service of Man (d) Fred W. Burgess, chats on Old copper and Brass (e) Peake, The Bronze Age and the celtic World (f) encyclopedia Britannica (g) American society for Metals, Metals Handbook, Desk edition, 1985 fORTUNATELY, MAN WAs sOON TO fiND, NOT sO MUcH A NEW METAL As A cOMBiNATiON Of cOPPER AND ANOTHER sUBsTANcE THAT GREATLY iMPROVED iTs UsEfUL PROPERTiEs.