Economical Processes.
In all silversmiths' establishments, the economical or waste-saving processes, as they are termed, require special and careful attention, so that the actual working loss, or that portion of it which is entirely irrecoverable by the manufacturer, may be reduced to the lowest possible degree. It may not be known to the general reader, or to the beginner in the precious metal trades, that there always takes place in the working up of the metal a loss of material, a portion of which the manufacturer is unable to recover, however cautious may be the means employed for that purpose. In the best regulated workshops, this loss will amount at the lowest estimate to about 2½ per cent. of the whole quantity worked up in the establishment. If the actual loss can be reduced to within the above limit it is considered very low, and highly satisfactory. Taking into consideration the loss that is occasioned in precious metal working, and from calculations that we have made from experience, we have long since arrived at the conclusion, that it cannot possibly be estimated under 10 per cent. of the total work daily performed; and this opinion is based upon experiments, the raw material being weighed before the process of melting and after the articles were completed, a fair calculation of course being made for unfinished work. This was including every description of manufacture; in some branches of the trade the working loss is not quite so great, but then there are others in which it is exceedingly heavy, so that the estimated loss in the jewellery trades cannot be safely put at a lower percentage than we have quoted.
It will thus be seen that the real loss, such as manufacturers are unable to recover by the means already known to them, amounts to one-fourth part of the total working loss of the establishment. This is easily accounted for: in the first place, a little takes place in the melting of the various alloys, the re-melting of scrap metal, the reduction of lemel, &c.; then there are the sundry manipulations of working; the passage of the metal through various acids, and the processes of finishing, each of which detaches small particles of metal, too small to be visible to the naked eye, but all of which go to form a portion of the loss which the manufacturer never recovers. The unrecovered metal may be judiciously proportioned as follows:—A portion of it works itself into the wood-work of the flooring of the shops, lathes, boards, and other parts of workshop appliances; then there is the refiner’s profit—as purchases of the sweep, polishings, and other refuse of precious metal workers. Instances can be recorded in which shrewd business-men have actually taken up the floors of their workshops and recovered a vast quantity of metal which was supposed to be lost for ever; and instances are well remembered in which two jewellers, upon removing into more extensive premises, availed themselves of the opportunity, not only of removing the boards which formed the flooring of the premises they were about to leave, but also those of the tenants they were about to succeed. In one case, metal of the value of £80 was recovered, and in the other it reached the large amount of £150. The two jewellers referred to, of course, were too un-English to refund the proceeds to the late tenants, who, when they became aware of it, if ever they did, would be, no doubt, wiser if sadder men.
To prevent the precious metal from finding its way into such places as these, it is advisable to have the floors well protected with sheet zinc or iron, in which case not the least particle could be lost in this manner. The extra cost of laying the floors would soon be amply repaid, by an extra quantity of the working loss being recovered; and if other equally effective precautions were adopted in the waste-saving processes by precious metal workers, the real loss, which they cannot avoid suffering, might even yet be reduced to the lowest possible point. Iron or zinc covered floors may be protected from wear, by laying over the surface small square grates of perforated iron, and these, being removable, may be readily taken up at stated periods, for sweeping the refuse from the floors; once a month will be found often enough to do this. The gratings should, however, be swept over lightly every day in order to remove the dust and particles of metal that may accumulate upon the surface into the perforations, and also for the removal of waste paper and other rubbish, continually accumulating in workshops.
Floors containing no such waste-saving precautions, are commonly swept over once, and sometimes twice each day, the refuse arising therefrom being carefully passed through a very fine sieve, all extraneous matter removed, and the residue remaining in the sieve being well sorted for the detection of all the precious metal visible to the naked eye. The whole refuse matter is then thoroughly burned in a muffle provided specially for the purpose, and finally reduced to a fine powder in a cast-iron mortar. When it has reached this stage of the process, it is quite ready for the particular kind of treatment it next receives at the hands of the refiner. Grinding by large stone rollers is now fast superseding this mode of pulverising jewellers' waste and refuse. When the latter plan is adopted, the refuse should be swept from the floors every morning, carefully looked through, and then transferred to a barrel (having the top removed, which may be used as a lid), where it can be well kept together, and hidden from view until the time arrives for its further treatment.
The waste which accumulates in the processes of polishing, lapping, &c., is greater than that already referred to, consequently, it cannot be too carefully looked after, in every stage, where a large manufacturing trade is being carried on in various branches. It is advisable in the practice of true economy, for the polishing, lapping, and scratching boxes to be repeatedly cleaned out, and the contents removed out of the temptation of every one, by being placed in a box, well lined with either sheet lead or zinc, which ensures the perfect safety of the material placed therein from all irregularities in the workshop. This kind of waste on being prepared for sale is again placed in a very strong wrought-iron box, made of a suitable size to fit the muffle, and having a thick close lid to it. After the work of the day has been completed, the fire in the furnace or muffle is made up, the dampers are closed, and then the iron box containing the refuse is at once passed in and allowed to remain there till morning, when every particle of matter will have become thoroughly burned; a slight pulverization after this process readily reduces it to a fine powder; further operations then cease, and the product is in all probability in a fine state of division, and fit for the subsequent operations of the refiner and assayer, whose special business it is to attend to these arrangements of precious metal workers.
The next process we have to consider is one which includes the whole of the liquid substances variously employed in silver-working establishments, such as the pickling solutions, washing-out waters, whitening mixtures, and waste or spent solutions of every kind. The whitening solutions or mixtures, when in use, should be kept apart from the ordinary cleansing liquids, as after they have been in use for a time, they become saturated with copper taken off the work during the whitening processes; if the solution is then set aside for some time the copper eventually crystallizes out from the liquor, which may be poured into the waste-water tub, and the remaining crystals of sulphate of copper, for such it then is, may be removed and preserved.