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The photographic news
- Bandzählung
- 27.1883
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- 1883
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- Hochschule für Grafik und Buchkunst Leipzig
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- Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 1296, July 6, 1883
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Zeitschrift
The photographic news
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Band
Band 27.1883
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- Titelblatt Titelblatt I
- Register Index III
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Band
Band 27.1883
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July 6, 1883.] THE PHOTOGRAPHIC NEWS. 419 sensitiveness of the latter only becoming traceable when chemical development is resorted to. Notwithstanding this, the indigo-sensitive bromide (collodion) is reduced to the metallic state with much greater facility than the blue sensitive (gelatine) modification. One might be disposed to expect the sensitiveness under the action of a reducing developer to be in some measure proportional to the reducibility of the compounds ; but Dr. Vogel points out that the sensitiveness is rather proportional to the capa bility of the respective bromides for absorbing radiant energy, as evidenced by their behaviour when subjected to the action of the solar spectrum. Dr. Vogel’s investigations will have to be taken into account in all efforts to realise the extreme sensitiveness of the gelatine plate when a collodion emulsion is used ; and it is quite probable that a notable future exists either for collodion emulsions, or for collodio-gelatine emulsions of the kind now so universally associated with the name of Dr. Vogel. We would remind our readers that on p. 378 of the present volume will be found full working directions for making the Vogel composite emulsion. In this pre paration, the bromide exists in the blue-sensitive condi tion, or as in the ordinary gelatine emulsion. GLASS. Sixth Article. The furnace figured on page 226 is not the only type used in the manufacture of window-glass ; it represents the form of nine-tenths of the Belgian furnaces, but there are in use in England and elsewhere other forms, such, for instance, as Siemen’s regenerative gas-furnace, and the so-called tank furnace of the same inventor. It would be difficult to explain, without numerous drawings, the details of construction and the functions of these distinct departures from the regular type of coal furnaces. In the gas-furnace, instead of the fuel being burned in actual contact with the pots, it is roasted in a separate producer, and the gas given off by the roasting of the coal is led—smoke tar and every other impurity ns well— to the furnace in which it is ignited. The gas so used con tains all the heat-producing properties of the coal—unlike the purified illuminating gas we burn in our houses—and is therefore, much more effective than street gas, besides being much less costly. The flame, after impinging upon and circulating round the pots, is caused to give up most of its heat by being drawn through a large underground chamber filled with a sort of honey-comb of fire bricks. According to the activity of the furnace these become intensely heated, and then, by a set of valves, the directions of the gas and air currents are reversed, passing up through the net-work of intensely heated fire-bricks and entering the furnace as a white-hot blast, the heat of which has been known to break down the pots and melt the arch of the furnace. The theory and action of the regenerative gas furnace is very beautiful, and there is, perhaps, no finer sight than to see a well-planned gas furnace at work. The system is also applied to what are called tank-furnaces. In these, the use of pots is avoided; the “ tank ” is, in fact, a large rectangular chamber, whose floor and walls are built of fire-brick ; the tank occupies the space under the furnace crown where the pots would stand in a pot furnace, and the vitrifiable materials being placed therein, the heat and flame pass over the top thereof, whether the furnace be worked by gas or by coal. Some of the tank-furnaces contain many tons of glass, and, by a later modification of the tank system, the process becomes a continuous one, for, by extending the area of the furnace, the inventor divides the tank into three compartments ; in the first the materials are melted, and the liquid glass flows into a second tank to clarify or become fine, and then passes to a third division, where it is ready for the blowers, and this process goes on without cesiation, night and day, by employing changes of men, for as long as the furnace will hold together. The continuous system, when fairly started, is probably the most economical method of glass-making at present in vogue. Of course, the first cost is great, as the work has of necessity to be very good, elaborate, and costly ; but after wards, in the saving of pots, economy of time of the blowers, continuity of the uniform beat to melt the materials, and, perhaps less total wear and tear than in pot furnaces worked by cr als, the producing power of a given furnace costing a ceitain sum is greater in ratio than a furnace costing a little and worked on the system explained in our last article. The tank system is applicable chiefly to the manufacture of the lower qualities of window glass (sheet-glass), also of rolled plate-glass, and especially of bottles. Up to the present time the finer descriptions of window-glass are rarely produced from tanks, and the system is not applicable to the method, now followed, of making plate-glass, for plates are cast by pour ing the contents of a pot on to a large iron casting table ; hence pots or crucibles must be used. The advantages of the regenerative gas furnace are supposed to consist in an economy of fuel, conjointly with a greater production, and the manufacture of an article of purer colour than by the use of coal in furnaces such as figured in our last. Tanks are in operation at two or three English works, and are turning out very good glass ; the difficulties usually ex perienced are seediness of the metal, stones, stri, and frequently a harsher product than if the same materials had been founded in pots. In the manufacture of common bottles (black porter bottles), and even the better sorts, such as lemonades and sodas, the tank system is pre eminently suitable, for quality is not of much moment; and seeing that common bottles are made from the greatest rubbish, it becomes a question as to how cheaply the material can be melted, especially when we consider that carriage has to be paid hundreds of mjles, and bears a con siderable proportion to the entire value of the finished article. A tank furnace is in existence, which is built but a few yards from the bank of one of our north country rivers, where the space necessary was levelled to begin building operations. The fuel arrives in boats, and is ‘all but at the turnace mouth, when it is thrown on to the quay. The material from which the bottles are made consists mainly of the hill-side, which is dug away as they require more room for building, and wheeled to the tanks, into which it goes along with limestone and the commonest alkali procurable ; heat does the rest, and the resulting bottles are excellent. The bottles are then packed into the holds of the boats that bring the materials and go away, ultimately to penetrate to the remotest corners of the habitable globe, wherever anyone can be found who cares for Bass’ bottled bitter beer 1 A project was started a few years since of utiliz ing the slag of blast furnaces for the manufacture of glass articles, such as bottles, and this was actually worked out in a factory which was erected in close proximity to some iron-works, whence the slag was con veyed white-hot to the glass furnace, and there worked up into bottles, by being mixed with some slightly better materials, yielding a workable glass. It is evident that a great saving of fuel could be effected by such an installa tion as this, and it is difficult to imagine what might not be the ultimate field for such an industry, for if glass could be cheaply fashioned in like manner to concrete blocks or castings of pig-iron, its employment in the arts of building and construction, and in sanitary work, would become a matter of course. The tank system met with severe opposition on its in troduction, as did the gas-furnace, and opinions are yet divided as to the merits and demerits of these systems over the older-fashioned one of pot-furnaces fed with coals. Gas-furnaces and tanks are costly experiments ; a fortune has to be sunk before a complete plant can be put down and good glass made therefrom. We know of cases where
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