[A]The above weights were lbs. sustained by 0·787 of a line in diameter, in wires of the various metals.
[A]The above weights were lbs. sustained by 0·787 of a line in diameter, in wires of the various metals.
CHAPTER VI.[A]
Various Qualities of Silver.
[A]See observations on Depreciation of Cost Price of Silver in Preface to Fourth Edition (pp. vii, viii), and the new Table of Cost Prices of Alloys in this Chapter, following the Preface (p. ix).
[A]See observations on Depreciation of Cost Price of Silver in Preface to Fourth Edition (pp. vii, viii), and the new Table of Cost Prices of Alloys in this Chapter, following the Preface (p. ix).
The chemical and physical properties of fine silver having been dealt with in a preceding chapter, we shall not refer to them again in detail; but, as we have already observed that it is sometimes employed inits purestate for special purposes, it is desirable that we should point out the uses to which it has been applied, especially those of a mechanical nature. With reference to the latter part of the subject we will now proceed to describe the commercial utility of the metal.
One of the greatest demands for pure silver—if not the greatest of all—is in the manufacture of fine filigree work, a branch of industry extensively practised on the Continent. This kind of silversmith’s work was attempted to be revived in this country during the years 1864-5, Birmingham and London being the principal placeswhere the manufacture was carried on; but the success of the undertaking as a staple industry must, at the most, have been only a partial one, for it soon declined, and the trade was thus virtually left, as before, in the hands of our Eastern competitors; most of whom produce splendid specimens of the art of filigree and fine wire-working. In India this work is wonderfully performed, and it is truly marvellous to witness the beautiful handiwork of the natives who practise this craft. Their productions are quite the work of the true artist, almost every article representing Nature in some of her various forms, such as flowers, animals, serpents, &c., and these are so skilfully imitated that no one could possibly dispute either the faithfulness of the representation or the ability of the workman. This is all the more surprising, because in India the natives have not the modern mechanical appliances which we possess in this country. The jeweller there represents to some extent our travelling tinker, only with this difference, that the travelling tinker in this country is generally an inexperienced and unskilful workman, whereas the Indian, if we are to judge him by his work, must be just the reverse.
Filigree wire-work is manufactured in Italy, Germany, Norway, and Sweden, and the secret ofthese countries maintaining the monopoly in this branch of the silversmith’s trade is that labour there is cheap; and not in any sense because English workmen cannot make the articles in question. It is owing to this cheapness of labour and the inexpensiveness of living that our Continental competitors can beat us by underselling us in the market; and to no other cause can the production of the foreign cheap article be assigned.
In India the art of working in silver and gold has long been practised, and so particular are the workmen there about the absolute purity of the metals they use, that they refine them by melting five times, under a very strong blast heat, before commencing the work of manufacture. The principal places where these art-manufactures are carried on are in Southern India and at Trichinopoly; and in these districts the delicacy and intricacy of the workmanship are brought to the greatest possible perfection. The articles produced there are all “hand-made,” and wrought entirely with a few simple tools, such as a hammer and an anvil (both of which are highly polished and burnished), a few fine pliers, blow-pipes, burnishers, scrapers, a pair of fine dividers, and some delicate scales and weights; these, with a fewperforated steel-plates for drawing the wire through, comprise the chief appliances of the travelling native jewellers. The process of the work is very simple. It is commenced by hammering out the metal upon the anvil, and when it has assumed a certain degree of thinness the dividers are next brought into requisition to mark it into certain widths, which are subsequently cut into strips and drawn into very fine wire through perforated steel-plates, a pair of strong pliers being used for the purpose. The holes in the steel-plates consist of graduated sizes, and by this means the strips of metal are soon considerably reduced; and when the proper thinness has been attained the wire is ready for the exercise of the practical skill and dexterity of the artisan, who produces from it the best filigree work in the world. Most of the native jewellers have books containing a variety of designs, but they more commonly work from memory, without any reference to patterns.
The principal localities where this description of work is produced in the highest perfection are Delhi, Cuttack, and Trichinopoly, in India; and Genoa, Paris, Florence, Malta, Norway, and Sweden. The Indian filigree work is the finest and cheapest in the world. The Maltese manufacture a very good kind, and their crosses are much admired;so also do the Chinese and Japanese, but the manufactures of these latter countries are not so tasteful as those of India, consequently they have not been so highly appreciated. Norway and Sweden produce filigree work of a very light weight; but still their productions in this art will not compare in regard to effect with the finest specimens from India.
We have said that the silver employed by the filigree worker should be in every case absolutely pure; because, when it is quite fine, it is extremely soft and pliable, so that it will remain in almost any form the artist may choose to work it, without that springiness which is found in all alloyed metals. However small might be the amount of alloy contained in the metal, the least admixture of it would produce an elasticity in the wire when pressed into form which would make it unworkable for fine filigree purposes; and in this state it would be the utter bane of the workman, as his progress would be altogether impeded in the production of his work. It is of the greatest importance that the spirals, and all the various forms required in filigree working, should remain steadily in their places when pressed into shape, without that rebounding which happens in the case of metals of an elastic nature, and in consequence of which noreally first-class work can be performed in connection with this art. For such reasons as these it will be at once palpable even to the ordinary reader that fine silver should always be used in preference to alloyed in the manufacture of filigree work.
The various ornaments of the filigree kind are commonly enclosed in a rim of plain and somewhat stronger wire, which gives additional strength to each part; and, when put together, tends to compose an article of considerably greater durability. In England these outside rims consist exclusively of sterling or standard silver, whilst all the inner work is of the finer material.
There are several methods of preparing the wire called “filigree.” The oldest and the one almost invariably practised in India consists in the first place in drawing down the wire in a circular form until the very lowest possible thinness has been attained, and frequently annealing it during the process, which is done by heating it to a red heat in a muffle placed upon an iron or copper pan. When this process has been effectually performed the wire is taken (if of the proper degree of thinness) and doubled together; these two fine wires are then twisted into one cord, which should be of the fineness desired. The wire requires annealing more than once during the process of twisting, andwhen it is completed it has a corded appearance, it is then ready for the manufacture of the various articles comprised in this kind of work.
The old plan of twisting was accomplished in the following manner. One end of the doubled wire being firmly secured in a vice or some other suitable instrument, so as to prevent it from turning round and so prevent the progress of the work, the other end of it was also firmly secured in a small hand machine or vice, which was made to revolve by turning a small handle with the right hand, the machine being held and regulated with the left, in order to keep the wire out at its full length so as to avoid knotting in the various parts of it; it was in this manner that fine filigree wire was in the first instance made.
The second plan was somewhat different, and in regard to the last part of the process it was certainly a great advantage, especially in the saving of labour, as a greater quantity could be prepared in a much less time than by the old method, that being slow in its progress. Here the lathe was made to supply the place of the small hand machine, the speed of which soon brought about the object in view.
The flattening of this twisted wire has now commonly come into use, and is effected by passingit through small steel rollers, hardened and polished. The object of this is soon manifest, as the labour-saving process is brought prominently into play: the wire in the first place need not be so finely drawn, and secondly the same filigree surface can be made to appear upon the articles as before, by securing the edges of the wires which show the filigree uppermost; and this is always the case in manipulating with this kind of wire. This method is generally in vogue with most filigree workers.
A third plan of preparing the material for the manufacture of filigree work is, we believe, due to the ingenuity of a celebrated Birmingham firm, who extensively practised this kind of work some years ago. The secret is not now generally known to the trade, therefore a few observations bearing upon it will not be unacceptable to those for whose benefit we are writing. The process is commenced in the same manner as before, in the preparation of the round wire, though this need not be drawn so fine, because by this method we have no twisting. When the round wire has arrived at the proper size it is flattened in the manner already explained; and when this is done it should be annealed, but experience will dictate best when this particular process should be carried out.After this latter operation the wire is submitted to the action of very small rollers, and bearing the pattern required in small grooves of various sizes. The pattern takes effect upon the edges of the wires only, and resembles the milled or serrated edges of our coinage, only of course the latter bears no comparison with regard to fineness. Lastly, the wire is again passed through the flattening rollers, and then it is ready to be worked up into the object desired.
Having gone through the general details of filigree working we shall next direct our attention to the component parts and commercial uses of the English standards, together with those of some other countries. In England there are two silver standards, called respectively the old and the new standards. They are as follows:—
Fine silver per lb. troy.
The older of these appears to have been always the legally recognised standard for the coinage, and also for the manufacture of plate. By a law passed, however, in the reign of William III. (1697) it was raised to 11 oz. 10 dwts. of fine silver in the pound troy weight. The manufacture of silverarticles from this standard was soon found to be not so durable as those made under the older one; consequently the silversmiths were permitted by a law passed in the reign of George III. (1819) to manufacture from the former standard of 11 oz. 2 dwts., the use of the new one being likewise permitted for the benefit of those who chose to avail themselves of it; and to this day it remains an English standard, though hardly ever employed.
By the Silver Coinage Act (10 Geo. 5), the fineness of the British coinage was reduced on account of the increased price of silver bullion; and the silver coinage now consists of one-half silver, one-half alloy, one troy pound of silver being coined into sixty-six shillings. The copper which composes the alloy in the silver coinage hardens the material employed, and it is found to wear better.
In order to make the matter as simple as possible, we purpose giving a few practical alloys, as follows:—
Old standard silver alloy, cost 4s.4d.per oz.
If it is intended that the above alloy should be for Hall-marking, it will be advisable to add a little extra silver to the prepared composition, because fine silver purchased from the refiner or bullion dealer is never absolutely pure, consequently the work will not pass the Hall; or better still alloy as follows:—
Old standard silver for Hall marking.
The new standard silver is composed of 38-1/3-40ths of fine silver and 1-2/3-40ths of copper alloy; or millesimal fineness 959 parts of fine silver and 41 parts of copper per 1,000 parts; the remedy being as before 0·004 parts.
New standard silver alloy, cost 4s.6d.per oz.
New standard silver for Hall marking.
Quality commonly used in England.
The qualities of the silver employed by the English silversmiths are invariably below the standard, the duties, assay charges, and loss of time in sending the work to the Hall to be marked acting as a great drawback to the trade in the midst of the keen competition of the present day. Silver chains, brooches, buckles, collarets, &c. are for the most part manufactured from inferior metal. In fact, some manufacturers positively refuse to make Hall-marked goods, on account of the great drawbacks attending the marking.
The alloys of silver are not calculated on the carat system, like gold, but by certain numbers, or other distinctive features, well understood by the particular firms which trade in silver wares. For our present purpose it will be sufficient to distinguish them by using the numerals, 1, 2, 3, 4, &c.; the alloy nearest approaching sterling or standard we shall call No. 1, and so on downwards until the lowest quality has been reached. We may state that silver does not lose its whiteness if not alloyed below equal quantities of thetwo metals; however, the alloys used in manufactures seldom reach so low a limit.
Silver alloy No. 1, cost 4s.2d.per oz.
Silver alloy No. 1, same as above.
Silver alloy No. 2, cost 3s.9d.per oz.
Silver alloy No. 2, same as above.
Silver alloy No. 3, cost 3s.6d.per oz.
Silver alloy No. 3, same as above.
Silver alloy No. 4, cost 3s.3d.per oz.
Silver alloy No. 4, same as above.
Silver alloy No. 5, cost 3s.2d.per oz.
Silver alloy No. 5, same as above.
Silver alloy No. 6, cost 3s.1d.per oz.
Silver alloy No. 6, same as above.
Silver alloy No. 7, cost 3s.per oz.
Silver alloy No. 7, same as above.
Silver alloy No. 8, cost 2s.10d.per oz.
Silver alloy No. 8, same as before.
The qualities of the silver alloys have been reduced in this list to various values, and the latter ones are as common as it is possible to make them, without a great and perceptible change of colour taking place in the prepared material. But if it be desired to work a still more inferior metal, then another ingredient must enter into its composition, in order to keep up the whiteness of the silver; and this other metal employed is nickel, the alloys with which we shall have occasion to refer to hereafter. Suffice it to say, however, that these inferior alloys of silver, prepared with nickel, are not now much employed by silversmiths in their art-manufactures. It will be observed that we have recommended the employment ofshotcopper in the manufacture of silver alloys: we do so for two reasons—first, because it can be purchased at a considerably cheaper rate than can the ordinary forms of copper, costing only one shilling per lb., whilst the ordinary prepared copper for alloying will cost double that amount; and, secondly, if proper attention has been given to the melting and casting process, the workable qualities of the metal will be found everything that could be desired. Therefore an excellent material in all respects can be produced by the means suggested at half the cost of alloy. A considerable saving to a largefirm might thus be easily effected by its employment.
In France there are three silver standards—two to be employed by silversmiths, and one for the coinage, as follows:—
Fine silver per lb. troy.
It will be seen from the above table that pre-war coinage in France did not represent the highest standard, and also that their principal one was inferior to our highest standard. French coinage contained 36-40ths of fine silver and 4-40ths of copper alloy, or millesimal fineness 900 parts of fine silver and 100 parts of copper per 1,000 parts of metal; the highest standard for silver wares contains 38-40ths of fine silver and 2-40ths of copper alloy, or millesimal fineness 950 parts of fine silver and 50 parts of copper per 1,000 parts of metal; the lowest French standard for silver wares contains 32-40ths of fine silver and 8-40ths of copper alloy, or millesimal fineness 800 parts of fine silver and 200 parts of copper per 1,000 parts of metal. The remedy is millesimal fineness 0·005.
French alloy for coinage, 4s.2d.per oz.
French alloy for plate, 4s.5d.per oz.
French alloy, lowest standard, 3s.9d.per oz.
In the preparation of these alloys with French silver it is undesirable to make any addition of fine silver, in order to enable goods manufactured from them to pass the Hall in safety, because the former is assayed before it leaves the bullion dealers, and the bars of metal are marked with their various standards. Such is not the case in England, andrefiners' fine metal is sometimes two or three grams under what it is supposed to be; hence the necessity for the further addition of some fine metal as we have already pointed out, when the object in view is to have goods Hall-marked; without which addition it cannot be effected.
In Germany there are four silver standards—one for the coinage, and three to be employed in the manufacture of silversmiths' wares; and in that country the various standards are severally applied in the production of fine filigree and other artistic work. The fineness of the standards is as follows:—
Fine silver per lb. troy.
As regards the alloy to be employed in the manufacture of these various qualities, copper only must be used, all other metals being forbidden. These standards represent all home manufactured articles of silver having reference to the standards of that country, as lately appointed by law.
German pre-war coinage was the same as French and contained 36-40ths of fine silver and 4-40ths of copper, or millesimal fineness 900 parts of fine silver and 100 parts of copper per 1,000 parts ofmetal. The highest standard of all is used for silver wares, and contains 38-40ths of fine silver and 2-40ths of copper, or millesimal fineness 950 parts of fine silver and 50 parts of copper per 1,000 parts of metal. The next German standard for silver wares contains 32-40ths of fine silver and 8-40ths of copper, or millesimal fineness 800 parts of fine silver and 200 parts of copper per 1,000 parts of metal. The commonest German standard employed by the silversmiths of that country contains 30-40ths of fine silver and 10-40ths of copper, or millesimal fineness 750 parts of fine silver and 250 parts of copper per 1,000 parts of metal indicated. Remedy 0·003.
Silver alloy for the German coinage.
Alloy for silver wares of the first standard.
Alloy for silver wares of the second standard.
Alloy for silver wares of the third standard.
Silver goods manufactured according to these standards in Germany, which have recently become law, may be alloyed only with copper, and any foreign substance is not allowed to enter into their composition. The remedy permitted in the actual fineness of the silver must not be under three thousandths of the standard specified. The goods to be stamped with the number of thousandths and the name of the manufacturer of them, and the correctness to be certified by the firm named. Experts are appointed by the Government to test this correctness, and if the provisions of the law have been justly observed a government guarantee mark is applied to them.
CHAPTER VII.[A]
Silver Solders: their Uses and Applications.
[A]See observations on Depreciation of Cost Price of Silver in Preface to Fourth Edition (pp. vii, viii), and the new Table of Cost Prices of Alloys in this Chapter, following the Preface (p. x).
[A]See observations on Depreciation of Cost Price of Silver in Preface to Fourth Edition (pp. vii, viii), and the new Table of Cost Prices of Alloys in this Chapter, following the Preface (p. x).
Soldering as applied to silversmith’s work is an art which requires great care and practice to perform it neatly and properly. It consists in uniting the various pieces of an article together at their junctions, edges, or surfaces, by fusing an alloy specially prepared for the purpose, and which is more fusible than the metal to be soldered. The solder should in every way be well suited to the particular metal to which it is to be applied, and should possess a powerful chemical affinity to it; if this be not the case, strong, clean, and invisible connections cannot be effected, whilst the progress of the work would be considerably retarded. This is partly the cause of inferior manufactures, and not, as frequently supposed, the want of skill in the workman.
The best connections are made when the metaland solder agree as nearly as possible in uniformity, that is, as regards fusibility, hardness, and malleability. Experience has proved, more especially in the case of plain and strong work (or work that has to bear a strain in the course of manufacture), that the soldering is more perfect and more tenacious as the point of fusion of the two metals approaches each other; the solder having a greater tendency to form a more perfect alloy with the metal to which it is applied than under any other conditions. The silver or other metal to be operated upon by soldering being partly of a porous nature, the greater the heat required in the fusion of the solder the more closely are the atoms of the two metals brought into direct relationship; thus greater solidity is given to the parts united, and which are then capable of forming the maximum of resistance. It is thus obvious that tin should not be employed in forming solders possessing the characteristics we have just described, for being a very fusible metal it greatly increases the fusibility of its alloys; but when veryeasysolder is required, and this is sometimes the case, especially when zinc has been employed in the preparation of the silver alloy, its addition is a great advantage when it comes to be applied to the work in hand. Solders made withtin are not so malleable and tenacious as those prepared without it, as it imparts a brittleness not usually to be found in those regularly employed by silversmiths; for this reason it is advisable to file it intodust, and apply it in that state to the articles in course of manufacture.
The best solders we have found to be those mixed with a little zinc. These may be laminated, rolled or filed into dust; if the latter, it should be finely done, and this is better for every purpose. Too much zinc, however, should not be added under any conditions, as it has a tendency to eat itself away during wear, thus rendering the articles partly useless either for ornamental or domestic purposes earlier than might be anticipated. Solders thus prepared also act with some disadvantage to the workman using them, for they possess the property of evaporating or eating away during the process of soldering, leaving behind scarcely anything to indicate their presence; consequently the workman has to keep on repeating the process until the connection is made perfect, which is always done at the expense of a quantity of solder as well as loss to the workman as regards time.
Solders made from copper and silver only are, generally speaking, too infusible to be applied to all classes of silversmith’s work.
Solders are manufactured of all degrees of hardness; the hardest of all being a preparation of silver and copper in various proportions; the next being a composition of silver, copper, and zinc; and the easiest or most fusible being prepared from silver, copper, and tin, or silver, brass, and tin. Arsenic sometimes enters into the composition of silver solders, for promoting a greater degree of fusion; and we have heard of workmen actually refusing to work with any other solder. The employment of arsenic has, however, a tendency to slightly endanger the health of those persons using it in large quantities; and of late its employment has not been persevered in.
In applying solder of whatever composition it is of the utmost importance that the edges or parts to be united should be chemically clean; and for the purpose of protecting these parts from the action of the air, and oxidation during the soldering process, they are covered by a suitable flux, which not only prevents oxidation, but has also a tendency to remove any portion of it left on the parts of the metal to be united. The flux employed is always borax, and it not only effects the objects just pointed out, but greatly facilitates the flow of the solder into the required places. Silver solder should be silver of a little inferior quality to thatabout to be worked up. The various degrees of fusibility of the several solders are occasioned by the different proportions of the component parts of the elements which enter into their existence. For instance, a solder in which tin forms a component part will flow or fuse much sooner than one in which copper and silver alone enter into composition, or of one wholly composed of copper, silver, and zinc, or of silver and brass; therefore it must be understood that tin is the best metal for increasing the fusibility of silver solders, and for keeping up their whiteness. Nevertheless it should always be used sparingly, and even then drawbacks will present themselves such as we have already alluded to.
It is our intention to give a list of the various solders which have been usually employed with more or less success, so that the silversmith and the art workman will be enabled to select the one most suitable to the particular branch of his trade; and we contend, from experience in the craft, that success of workmanship mainly depends upon this point.
Hardest silver solder, cost 3s.9d.per oz.
Hardest silver solder, same as above.
Hard silver solder, cost 3s.6d.per oz.
Hard silver solder, same as above.
Easy silver solder, cost 3s.2d.per oz.
Easy silver solder, same as above.
The silver solders here given are not such as we can confidently recommend to the general silversmith, having proved them to be very unsatisfactory in certain classes of work. For example, the first solder, except in the case of plain strong work, would be far too infusible to be generally used by the silversmith; the second, although much more fusible, cannot safely be applied to very fine and delicate wire-work, because the brass in its composition is so uncertain: unless specially prepared by the silversmith, it probably, if purchased from the metal warehouses, contains lead; the latter is injurious, and in process of soldering it burns and eats away, much resembling the application of burnt sawdust to the work. No really effective work can be produced when the above symptoms present themselves. The same remarks apply to No. 3, which is the most fusible, and when free from lead or other base metal it may be classed as a tolerably fair common solder. In the preparation of the solders to which we are alluding, it is preferable to employ, instead of thebrass, a composition consisting of a mixture of copper and zinc, in the proportion of two parts of copper to one part of zinc; the operator then knows of what the solder is composed, and if it should turn out bad he will partly know the cause, and be able to supply a remedy.
The solders that we have found to answer our purpose best are composed of the following elements. The first is described again ashardsolder, but it is not nearly so hard as the one previously described.
Best hard silver solder, 3s.9d.per oz.
Best hard silver solder, same as above.
Medium silver solder, 3s.6d.per oz.
Medium silver solder, same as above.
Easy silver solder, 3s.3d.per oz.
Easy silver solder, same as above.
Common silver solder, 3s.per oz.
Common silver solder, same as above.
The whole of the above-named solders will bleach or whiten properly if applied to silver of the suitable quality for such purposes. We have used copper and spelter in our silver solders, because we have found from experience that the fewer number of times a solder is melted the better it is for all purposes. This result of our experience is in direct opposition to those authors who have professed to treat upon this subject, and who can have had but a small amount of real practical knowledge, for it is argued by them that the oftener a solder is melted the more properly does it become mixed, and, consequently, the more fit is it for the workman’s use. To such argumentswe are prepared to give a blank denial, and our reasons for so doing we will state further on in this treatise.
There are various other silver solders used by silversmiths; some few of which it will be as well perhaps, while we are on the point, to enumerate:—
Silver solder for enamelling, cost 3s.9d.per oz.
Silver solder for enamelling, cost 3s.2d.per oz.
Easy silver solder for filigree work, cost 3s.9d.per oz.
Quick-running silver solder, cost 3s.per oz.
Silver solder for chains, cost 3s.per oz.
Easy solder for chains, cost 3s.per oz.
Common silver solder, cost 2s.9d.per oz.
Common easy solder, cost 2s.9d.per oz.
Silver solder with arsenic, cost 3s.9d.per oz.
Silver solder with arsenic, cost 3s.6d.per oz.
Easy silver solder, cost 3s.2d.per oz.
Common easy solder, cost 2s.9d.per oz.
Another common silver solder.
A very common solder.
The solders here given will be found amply sufficient to select from, for every operation of the silversmith, and will answer the several purposes for which they have been described. When tin and arsenic are employed in the composition of solder, either together or separately, they should be withheld until the more infusible metals withwhich they are to be united have become melted; the tin or tinsel should then be added, and when this is well melted with the mass, fling on the top the arsenic, let it melt, stir it well together, and pour it out quickly into an ingot mould already prepared for its reception.
When silver and brass, or silver and composition, alone form the component parts of the solder, these metals may be put into the melting-pot together, well fused, stirred, and poured out as before.
Solders into which volatile metals enter, upon repeated meltings, become hard, brittle, and drossy, and are therefore not so good as when the metal has received only one melting; it is for this reason that we have always preferred to manufacture our solders from metals which have not been melted before, or from those which have gone through the process as few a number of times as possible.
The mode of soldering gold and silver is as follows: Take the solder and roll it out thin between the flattening rollers, or file it into dust, according to the kind of work in hand. If filed into dust, it is all the better if done very fine; and if reduced to a flat state, which should be tolerably thin, cut it into little bits, or pallions, which may easily be performed with a pair of hand-shears,length-ways and afterwards cross-ways. When this is done, take the work which is to be soldered, join it together by means of fine binding-wire (very thin iron wire), or lay it upon the pumice so that the joinings can come close together, and will not be liable to move during the process; wet the joinings with a solution of borax and water, mixed into a thick paste, applying it with a small camel-hair pencil; then lay the bits or pallions of solder upon the parts to be united, and having placed the article upon some suitable object, take your blowing instrument (Fig. 16) and blow with it, through a gas-jet, a keen flame upon the solder in order to melt it; this will render the unification of the parts complete and compact.