Chapter 4

In the table, T, there is a rectangular receptacle, _t_, containing rasped or powdered velvet for the purpose of forming a reverse of the dot. This powder attaches itself to the gum and imitates on the wrong side of the fabric a dot similar to that on the upper or right side. The velvet is wound upon the roller, _r_, and from thence passes under the guiding roller, _r'_, the punches, and the second roller, _r"_. These two latter rollers are solidly connected by a straight-edge fixed at the extremity of the lever, L, whose other end is in continuous correlation with the eccentric, M, which controls the lateral displacements; while the eccentric, O, actuates, by means of the screw, Q, and the ratchet-wheel, S, the longitudinal advance of the velvet. The eccentric, M, is fixed upon an axle, A', which carries a wheel, U, having teeth inclined with respect to its axis, and which derives its motion from the Archimedean screw, N, fixed at one of the extremities of the cam-shaft, A.

We have stated above that the maximum daily hand production of tulle dotted in quincunxes of 0.04 of an inch is about one yard. At the rate of 30 revolutions per minute, and for the same article as that just mentioned, this dotting machine is capable of producing, theoretically, 360 yards per 10 hours; but practically this production is reduced to about 250 yards, which, however, is sufficiently satisfactory.

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THE REPRODUCTION AND MULTIPLICATION OF NEGATIVES.

By ERNEST EDWARDS, B.A.

A question, relative to the subject of reproducing negatives, which was put at a meeting of one of your New York societies, prompts me to make a few remarks on the subject.

Among the numerous and widely diversified ramifications of our business (the Heliotype Printing Company) we have very often to reproduce and multiply negatives in both a direct and reversed form. Various methods for doing this have been tried, and I may here say that I am quite well aware of all the methods that have hitherto been suggested for the purpose, but that which I am to describe is the one to which preference has been given, and which is that known as the carbon process.

A sheet of carbonized paper or "tissue," having been sensitized by immersion in a bath of bichromate of potash, is dried in the dark and placed away for future use, although it is undesirable that it be kept for more than four or five days. This is placed in a printing frame in contact with the negative and exposed for a few minutes, after which it is immersed in water, squeegeed down upon a glass plate, and developed with warm water in the way so well known to carbon printers. The result is a transparency which, owing to having received a sufficient exposure, should show every detail of the negative. The nature of the tissue employed for such a purpose must be such as to give no strong contrasts, but everything reproduced with soft and fine gradation of tone.

The transparency thus obtained forms the _cliché_ by which the negatives are subsequently made; and a negative of any size may be obtained by the camera on wet or dry plates. The transparency must, of course, be pointed to the sky and the light transmitted through it, no other light being allowed to reach the lens except that which passes through the carbon transparency. Care must also be taken that the transparency is _uniformly_ lighted. If it is not possible to obtain a northern light, which is best, a reflector of white paper or card may be used which must be sufficiently large and placed at an angle of about forty-five degrees to the transparency.

If the repeated negative is to be of the same size as the original it may be readily produced by repeating the operation of printing on carbon tissue, using the transparency in place of the negative, or using a dry plate in place of the tissue. But on the whole I have satisfied myself that the best results are to be obtained by the first method. There is a greater softness in the latter method, but a greater character and similarity to the original in the former method. There is no doubt that the use of the carbon transparency removes the hardness and riffidness of the outlines peculiar to the older method of a collodion transparency, while with carbon as the medium it is difficult for any but the most experienced eye to distinguish the copy from the original.--_Photo Times._

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A NEW METHOD OF MAKING GELATINE EMULSION.

Since gelatine emulsion first came into use one of the greatest troubles in connection with the manufacture of it has been that of washing. According to the first methods the time taken for this part of the process was, I believe, about twenty-four hours. It was very much reduced and the ease of manufacture greatly facilitated by the methods now most generally used, and which were, I believe, first communicated by Messrs. Wratten and Wainright. I refer to those of precipitating with alcohol and of straining the emulsion, when set, through canvas, so as to divide it very finely. When the latter method is resorted to a comparatively short time is sufficient to wash it. This method, although a great improvement upon the older ones, yet leaves much to be desired, especially for those who are not in the habit of making emulsion regularly, but only an occasional batch. When the weather is at all warm it takes a long time for the emulsion to set, unless ice be used, and when once it is set the washing process is an exceedingly "messy" one unless the water be cooled with ice; and the amount of water taken up during washing is often so great that there is considerable difficulty in getting the emulsion to set on the plates. In fact, even in cold weather, it is not an easy process to conduct in the necessary near approach to total darkness.

Considerable suspicion has of late been thrown upon the thoroughness of the alcohol method, unless the emulsion has, previous to precipitation, been freed of the greater part of the soluble salts by washing; that is to say, it is doubtful whether the whole of the soluble salts can be eliminated by the process, and, therefore, unless in exceptionally hot weather, it would seem best not to trust to it, except as a further security against soluble bromide and nitrate after washing. Besides this, the consumption of alcohol is very large. Almost three times the amount of the emulsion precipitated is required, and this, even when methylated spirit is used, adds considerably to the expense. With a view of doing away with the washing altogether, or, rather, of washing of the silver bromide when not incorporated with the gelatine, several processes have been invented. By these silver bromide is obtained in a very fine state of division, ready to mix with gelatine and water in any proportion.

The best known of them is Captain Abney's very ingenious glycerine method, which seems to have been thoroughly successful in his hands, although it has not been in every one's. The silver bromide obtained by his process is not highly sensitive, and requires boiling with gelatine before it is in a fit state to make a rapid plate.

We have lately had described in these columns a method of obtaining bromide in a highly-sensitive state by means of the use of an acid, whereby, after emulsifying and boiling, the viscosity of the gelatine was destroyed, and the bromide in time deposited itself. During the late hot weather, when washing became almost impossible, I was led to cast about for some method of eliminating the soluble salts less tedious and "sloppy" than that of washing, more certain and less expensive than that of precipitating the whole of gelatine with alcohol, and which would take less time than the method of obtaining the bromide in a pure form.

My first idea was to make up the solutions used in emulsifying in a very concentrated form, and, after emulsifying, boiling, and allowing to cool, to add to the thin emulsion thus obtained gelatine to the amount of twenty grains to the ounce, and to precipitate this with alcohol, the rest of the gelatine required to make up the bulk being afterwards added, and the whole thoroughly incorporated by warming and shaking. I was thus successful in reducing the amount of alcohol required to one-third of what would be necessary if the whole of the emulsion were precipitated; but still I found that, if a reliable emulsion were required, the pellicle as formed had to be washed to free it from the last trace of soluble salts.

It now struck me that it might be possible to precipitate the bromide of silver direct from a very weak solution of gelatine, and obtain it in such a form that it might be filtered, washed, and in every way treated as an ordinary precipitate. I tried the following experiment. I took--

1. Silver nitrate....................... 200 grains Water............................... 1½ ounce. 2. Ammonia bromide...................... 120 grains. Water................................ 1½ ounce. Gelatine............................. 12 grains.

I emulsified the two together in the usual way, allowed the whole to cool, and then poured the thin emulsion into about ten ounces of alcohol, stirring the while. As I had anticipated, a flocculent precipitate was formed, which settled to the bottom of the vessel in a few minutes. This was, in fact, sensitive bromide of silver mixed with a very small quantity of gelatine (about five per cent.), and could, I found, be treated in the same manner as a bromide precipitate from an aqueous solution; it might be washed, either by decantation or by filtration, easily dried, and doubtless could, when dry, be kept for an indefinite time, and be at any time used by mixing with gelatine and water in any proportion thought fit.

I found that a less amount of gelatine than four grains to the ounce was sufficient to carry the bromide down, while five grains to the ounce carried it down in something which I considered too near an approach to a plastic mass.

It will be noticed that in the experiments which I have described the emulsion had not been boiled, so that the sensitiveness of the bromide was probably not great. As the experiment was done in daylight it was of no practical use for making emulsion; but I have since made several batches in this manner and have found them most satisfactory.

When sensitiveness is sought by boiling I rind it necessary to add a small quantity of gelatine after boiling and before precipitating, as that which has been kept for some time at a high temperature seems to have lost the viscosity necessary to carry down the silver bromide in such a form that it can he easily separated from the alcohol and water.

The practical manner of making an emulsion by this method may be as follows. Make up the following mixtures:

I. Silver nitrate...........................................400 grains. Water..................................................... 3 ounces.

II.

Ammonia bromide..........................................240 grains. Gelatine..................................................24 grains Water..................................................... 3 ounces. Hydrochloric acid enough to slightly acidify the solution.

III. Gelatine................................................. 20 grains. Water.................................................... ½ ounce. IV.

Hard gelatine (say Nelson's X opaque, or Mr. A. L. Henderson's)................................240 grains. Soft gelatine (Nelson's No.1)........................... 240 grains. Water.....................................................24 ounces.

Nos. II., III., and IV. are allowed to stand until the gelatine is softened. No. I is then warmed in a hock bottle until the gelatine is just melted, when No. II. is poured into it, a little at a time, with vigorous shaking, until the whole is emulsified. It is then transferred to an ordinary jelly can, which is placed in a saucepan half full of water over a ring Bunsen burner in the dark room, and boiled for half an hour. It is then allowed to cool to about 100° Fahr., when No. III. is added. The whole is then allowed to get quite cool, when it is poured, with stirring, into about one pint of methylated spirit. If it be wished the precipitate may now be filtered out and washed at once like an ordinary filtrate, but I prefer to allow it to settle, which it will do in about five minutes. The supernatant fluid is then gently poured off.

This fluid will have the appearance of still containing a considerable amount of the silver bromide; but if it be kept and filtered it will be seen that the quantity is really so small that it may be disregarded. We all know what an alarming quantity of silver seems to be going down the sink when we wash vessels to which a very small quantity of emulsion is adhering. If filtering be resorted to the liquid which comes through will be quite clear. This was somewhat unexpected by me, as, if an emulsion containing the whole of the gelatine be precipitated into alcohol in the usual way, the alcohol becomes milky with a substance which could not, I imagine, be filtered from it.

Two or three ounces of methylated spirit are now added to the vessel containing the silver bromide, and the latter well mixed with it. This makes the precipitate "firmer"--if such an expression be allowable--and this time it will sink to the bottom almost immediately after the stirring has ceased, and the alcohol may be poured off.

I consider that the bromide in this state is practically free from soluble salts, but it may be washed with one or two changes of water if desired.

No. IV. is now gently heated till the gelatine is melted and the precipitate mixed with it. It must be kept warm for some time, and shaken vigorously until all granularity has disappeared, This is, of course, ascertained by placing a drop of the emulsion on a piece of glass, and examining it. If it be wished to keep the bromide of silver for future use it may be placed on a piece of muslin stretched in the drying-box, when it will dry in a very short time; and, although I cannot speak from experience on this point, it will, I have no doubt, keep for an indefinite time so long as light is kept from it.

If it be desired the ammonio-nitrate method may be used instead of the boiling one, although in my hands it does not give such sensitiveness. If it be desired to use this method, solution Nos. I, II., and IV. are made up exactly as for the boiling method, except that No. II. is not acidified. Liquid ammonia is then poured with stirring into the silver solution, until it blackens and again clears. Emulsification is performed exactly as described above, but instead of boiling, the emulsion is kept at a temperature of about 100° Fahr. for half an hour, when it is poured into the alcohol, no addition of gelatine being previously made.

I think I may claim for the method which I have just described that it is less troublesome and more certain than either the ordinary washing method or the usual one of precipitating with alcohol, while it affords an easy method of making sensitive silver bromide in such a form that it can be more easily stored and afterwards manipulated than if it were in the form of pellicle. The whole of the soluble salts are eliminated, and also any gelatine which may have been destroyed in the cooking. The amount of alcohol used is comparatively small; in fact, to prepare silver bromide for a pint of emulsion very little more than a pint of methylated spirit is required. Besides this I do not think that I would be wrong in saying that the chance of green fog is reduced to a minimum.

Let me take this opportunity of thanking Captain Abney for his prompt reply to my question about the connection between the proportion of bromide to gelatine in emulsions, and the density of resulting images.--_W. K. Burton, in British Journal of Photography_.

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THE POTTERY AND PORCELAIN INDUSTRIES OF JAPAN.

Japanese chronicles claim that the first pottery was made in the year 660 B.C.; it was not, however, until the Christian era that the art made any considerable advances. In the year 1223 A.D., great improvements were made in manufacture and decoration of the ware. From that date to the sixteenth century the great potteries of Owari, Hizen, Mino, Kioto, Kaga, and Satsuma were established. The Rahn-Yaki, or crackled ware, was first made at Kioto, at the commencement of the sixteenth century. The best old Hizen ware, that which is still the most admired, was made at Arita Hizen, in 1580 to 1585; the old Satsuma dates from 1592. Consul-General Van Buren states that porcelain clays are found in nearly all parts of the country, and the different kinds are usually found in close proximity, and close to canals and rivers, which is of considerable advantage, as affording a means of transport. In all cases every variety of clay used in the manufacture of pottery is found in a natural state; there is no necessity to manufacture the quartzose or fusible clays as is done in other parts of the world, and which adds considerably to the cost of the ware. One of the peculiarities in the clay found in Japan is that it contains both the fusible and infusible materials in such proportions as to make a light, beautiful, translucent, and durable porcelain. At Arita, in Hizen, there is a clay found which contains 783/4 per cent, of silica, and l73/4 per cent, of alumina; from this clay is made the delicate, translucent eggshell ware, without the addition of any other matter. From an adjoining bluff a clay is taken which has 50 per cent, of silica, and 38 per cent, of alumina; from this the common porcelain is made.

Potter's clay is found in very large quantities in the provinces of Yamashiro, Hoki, Turoo Iyo, Hizen, Higo, Owari, Mikaera, Idyn, Musashi, and Mino. In the whole of Japan there are 283 localities where the clay is deposited; many of these only furnish inferior clays, but they are all fitted for use in some of the various kinds of pottery. These clays are thoroughly powdered by means of what is called "balance pounders," worked in some localities by water-power, but the work is often done by hand. The powder is then dried, and stored on boards or in flat boxes. This dough does not go through the process of fermentation. The shaping is almost exclusively done on the potter's wheel, which is set on a pivot working in a porcelain eye. As a rule, the wheel is turned by the potter himself, but in Hizen it is kept in motion by means of a band connected with its pivot and another wheel turned by a boy. In making dishes of other shape than round, a crude mould is sometimes used. After the clay has been shaped on the wheel, it is set away for drying, and usually in two or three days it is considered sufficiently dry for smoothing, which is done on the wheel with a sharp curved knife. The material is now made into "bisque," or biscuit, by a preliminary baking in small ovens, when it is ready for painting, if it is to be painted on the biscuit; if not, it is ready for the glazing. In either event it will then go to the large furnace for the final baking. The kilns for this purpose are always built on hill sides, and are joined together, increasing in size from the lower to the higher ones, and in number from four to twenty five; these kilns are so constructed that the draught is from the lowest one, in addition to which each kiln has its own firing place. The result of this construction is that the upper ones are by far the most heated, and the ware is arranged accordingly; that which requires the least baking, in the lower kiln, and that which requires the greatest heat, in the upper. These connecting kilns have the merit of being heat saving, but they are usually small and badly constructed, and the heat in none of them is uniform.

The glaze is made from the silicious clay and potash extracted from wood ashes. This potash is not a pure white, and this accounts for the dirty color usually to be observed in unpainted Japanese ware. In different districts the painting varies. For instance, in Owari, the greater part of the ware is painted a cobalt blue--the cobalt ore being found in the bluffs near the clay deposits, and is used for painting the cheaper wares, and for this purpose German cobalt is also employed. The painting with cobalt is generally done on the biscuit before glazing. In several districts a very handsome ware is made, and painted on the glaze. For this kind of painting the colors are mixed with a silicate of lead and potash, and baked the third time in a small furnace at a low temperature. The coloring oxides in use are those of copper, cobalt, iron, antimony, manganese, and gold. Japanese porcelain painting may be divided into two categories, decorative and graphic; the first is used to improve the vessel upon which it is placed, and this class includes all the ware except that of the province of Kaga, which would come under the head of graphic, as it delineates all the trades, occupations, sports, customs, and costumes of the people, as well as the scenery, flora, and fauna of the country. "Owari ware" is made in the province of that name; it is not as translucent, but stronger and more tenacious than some of the Hizen manufacture.

The principal potteries are at a village called Sèto, twelve miles from the sea; in this village there are more than 200 kilns. The ware is mostly painted a cobalt blue, and is merely of a decorative kind, consisting of branches of trees, grass, flowers, birds, and insects, all these being copied by the artist from nature. All the Owari ware is true hard porcelain, and is strong and durable. In Hizen, a number of wares are manufactured, the best known kind being the "Eurari," which is made at Arita, but painted at Eurari. The colors in use are red, blue, green, and gold; these are combined in various proportions, but, as a rule, the red predominates. Generally the surface of the vessel is divided into medallions of figures, which alternately have red, blue, or white back-ground, with figures in green or blue and gold.

The egg-shell porcelain sold at Nagasaki is made in this province from Arita clay, and this is made from clay with no admixture of fusible matter except that contained by the clay naturally. The province of Satsuma is noted for crackled ware. It is only within a very few years that large vases have been manufactured, and in earlier days the old ware was confined to small vessels. The glaze is a silicate of alumina and potash, and the best ware has a complete network of the finest crackles; the painting is of birds and flowers, and noted for its delicate lines of green, red, and gold.

In Kioto, the ware manufactured is very similar to that produced in Satsuma, but it is lighter and more porous; the decorations are also nearly the same, being of birds and flowers. There is a description of ware made in Kioto, called "Eraku," the whole body of which is covered with a red oxide of iron, and over this mythical figures of gold are traced. That produced in Kagja is _faïence_, and in the style of painting is unlike any other in Japan, the predominating color being a light red, used with green and gold. The designs with which it is profusely decorated are trees, grasses, flowers, birds, and figures of all classes of people, with their costumes, occupations, and pastimes. The "Banko" ware is made at the head of the Owari Bay; it is an unglazed stone-ware, very light and durable, made on moulds in irregular shapes, and decorated with figures in relief. On the island of Awadji, a delicate, creamy, crackled, soft paste porcelain is made. The figures used in decoration are birds and flowers, but outlined by heavy, dark lines.