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The photographic news
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- 27.1883
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- Bandzählung
- No. 1302, August 17, 1883
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The photographic news
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Band 27.1883
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- Titelblatt Titelblatt I
- Register Index III
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Band 27.1883
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August 17, 1883. J THE PHOTOGRAPHIC NEWS 525 wax is more firm and hard.” Tallow, however, can never be regarded as a good illuminant. Look at this clumsy apparatus of tray and snuffers, with the candle guttering in long winding sheets, every drop on the brass candlestick being marked by a green spot of ‘‘verdigris ” (stearate of copper); and the long red point of the unconsumed wick protruding from the dull brown flame, exhaling nauseous odours both from unburnt and burnt tallow. One would have imagined that such a candle would have fallen a victim to popular execration when Chevreul and Young provided their cheap and beautiful substitutes. But no, tallow candles are still burnt in tons—miners, cobblers, and other traditional craftsmen adhere to the light of their fathers— and so we cannot avoid entering into the details of their manufacture. It may be, perhaps, that the recommending qualities of tallow to certain classes are, the readiness with which it adapts its form to circumstances, enabling it to be stuck into any crevice, without bending, as cheap paraffin will, and the large wick, keeping alight in draughty places, and giving a bulky flame, without much smoke. Referring to old manuals of candle-craft, I find blendings of tallows recommended ; certain proportions of beef and mutton fat. The best brand for the purpose is known as P.Y.C., which, I believe, means Petersburg Yellow Candle (tallow implied). This article has lost its prestige of late years by the enormous imports of Australian substitute, and now appears to serve rather as a basis of speculation than in any commercial capacity. However, the tallow should naturally be as hard as possible, without risk of cracking, which result can only be attained by experienced selection. The fat from various portions of the animals is rendered, i. e., boiled well with salt (or acid) water till the fibrous portions have settled out, and the tallow swims white and sweet on the top. Of this, with no more ado, candles are made. A truly ancient form of tallow candle is the rush- light. As it is now, so it must have been thousands of years ago; it being impossible to figure a more primitive stage of existence than you see here. A rush, deftly stripped of its skin, of which a slender streak is left to act as a kind of backbone to the tender pith. A number being thus prepared, are allowed to become thoroughly dry, by hanging in an airy loft. They are then tied by the tops in little bundles of four or six, which are held in the hand, being kept apart by the intervention of the fingers. Thus disposed, they are discreetly immersed in the tallow, of a temperature just high enough to preclude solidifica tion in bulk, yet to insure a sufficient portion adhering to the cold rushes. After two or three dippings, the candle is complete. It remains now to let it harden and whiten, to which end it returns to the aforesaid loft, and in about a month of favouable weather is ready for sale. I had considerable difficulty in obtaining these specimens of rushlights, although my inquiries were made in the most out-of-the-way country places. In Hampshire, I came across this instrment, which is really interesting, and which I am told is still used in the Isle of Wight farms. A small deal strip is stuck upright at angles to a broader piece of wood, which acts as a firm basis. The upright board is furnished at the top with a rude iron clamp, which holds the long rush, dipped once or twice into grease. The rush, as you see, is held at an angle of 30° to the basis, on which the end rests, the ash dropping on the table. A more primitive candle stick and light cannot be conceived. But the rushlight itself I found, singularly enough, in the heart of London, where im prisoned in a tall gauze shade, it still illumines, in perfect safety from fire, many a humble sick chamber. One very good quality of this light is the absence of snuff; the wick consuming as it reaches the air, leaving nothing but a slight feathery ash. I cannot say when cotton wick was introduced. Oakum (^stuppa) and papyrus {scirpa) were the ancient substitutes ; but most probably, with us, the wicks were made of linen, gradually giving place to cotton, as that material became more familiar. All candles were “dipped,” “rolled,” or “poured,” till the Sieur de Brez, in the 15th century, introduced the “mould” candles, which rapidly asserted a position of superiority. Of these we cannot speak till the last lecture, and with regard to dipping, not much remains to be told. The principle remains the same ; but the pressure of increased consumption concurring with superior mechanical skill, brought about several improve ments in the method of working. The wicks were hung on hoops, and a row of three hoops on one arm of a revolving wooden star, so contrived that only three hoops at a time should pass over the kettle. Once in position, the craftsman depressed the arm with the three hoops pendant, which were withdrawn, on release, by the antagonistic weight of the opposite spoke. So with all the arms in rotation, and by the time the first came round again, the candles would be ready for another dip. The whole arrangement was suspended to one arm of a scale beam, which indicated when the candles had attained the legitimate thickness. This was a great saving of labour, but still each individual wick had to be cut and fastened to the hoop. A good method of obviating this is shown in this rectangular iron frame. To one corner I fasten the end of a wick on this reel. Adjusting the frame to a simple revolving appliance, I turn the handle rapidly, and you see the wick wound upon the frame. It is then secured tightly by a little clamp at either end, and a number of these frames adjusted to the revolving spokes already described. After one immersion, the wicks are rigid enough for independent action. Accordingly, a sharp knife is drawn along either row, at the base. Now, you see, the rudimentary candles swing loose, the lower parts of the frame is removed, and the dip ping proceeded with en regie. Another form of tallow candle is the “ flat candle,” a kind of twin, or two candles joined sideways, and flattened. This is much affected by cobblers, for no reason that I can see, except as alleged by a sutorial interlocutor of long experience, that it gives twice the light of an ordinary caudle—in which, as it has two wicks, there is, perhaps, nothing remarkable. The great fault of tallow candles, dips, or moulds, is their tendency to gutter, and to exhale evil odous when blown out; also, the necessity for snuffing them. The first two vices are in eradicable, lying at the root of the composition of tallow itself. Being a mixture of hard stearin and soft elaidin, the latter melts first, and consequently overruns the hard cup formed by the former, producing the domestic phenomenon of “ winding sheets.” Again, each of the commixts is a compound of fatty acid, stearic and elaic, with glycerine. This combination has to be split up, which operation, consuming heat, dims the light to begin with, and the malcombustible glycerine is vapourised as acrolein, a highly pungent compound. It remained for Chevreul to purge the candle from this abomination ; Mr. Palmer, how ever, took the wick in hand, and by a happy invention, rendered snuffing unnecessary. He introduced a fine thread (technically called the “doctor”), impregnated with impalpably powdered bismuth, into the body of the wick, which, further, was not twisted after the ordinary fashion, but consisted of a number of parallel threads bound together by another one wound round them. The bismuth fuses into a little ball, the weight of which draws the wick laterally out of the flame into contact with the air, having performed which duty, the bead oxidises, and votal- ises away. Here you have one of “ Palmer’s Metallic Wick Candles,” burning side by side with an ordinary dip, and the difference in burning renders comment superfluous. Mr. Palmer has very kindly supplied me with a number of wicks and candles of different structure, and for various purposes. In this large candle there are three convolute wicks. These were wound spirally round a rod, clamped at the top, the rod introduced into a mould—as here shown—the mould then filled with tallow, and allowed to cool, when the rod was withdrawn, leaving the wick round a tubulated passage up the centre. This kind of candle was much used in the candle lamp, of which I have here a very old specimen. You see the three wicks, untwisting as they burn, each with its b ight little head. The flame is large, but, owing to the reasons alleged before, not luminous in proportion. Later on, I hope to give you some numerical values of the luminosity of candle flames, which will show you the great differ ence in the burning of stearin with, and stearic acid without, glycerine. We have talked enough of tallow now, and shall discover nothing more to its advantage. By pressure, the softer elain may be, to a great extent, removed ; look at this brilliant, blue white substance, which you would hardly know to be tallow ; and, again, at this mould candle made from it, burning without guttering, and with a metallic wick. Still the light is dim and the smell evil. In our fourth lecture you will see, though, how the coarsest tallow can be made, by the chemists’ art, to rival paraffin in the brilliancy of light, spermaceti in whiteness, and wax in cleanliness, sweetness, and hardness. (To be Continued.} ROCHER’S PATENT FOR CONCAVING PHOTOGRAPHS. American Patent No. 267,720, dated November 21, 1882, Application filed August 14, 1882.
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