Candle, a cylinder of wax, paraffin, or fatty matter, inclosing a central wick, and intended for giving light. The chief raw materials employed in the manufacture of candles are wax and spermaceti for the more expensive kinds, and tallow, palm-oil, and paraffin for those in general use. Candles are made in three ways—viz. by basting and rolling, by dipping, and by moulding. The first method, basting followed by rolling, is employed in the case of wax, which cannot be moulded satisfactorily on account of its great contraction on cooling and the tenacity with which it adheres to the moulds. Dipping is employed in the case of tallow dips and the more modern 'snuffless dip' candles, both of which are used when a large flame is desired that is not readily extinguished in a draught. The bulk of the candles in use are made by the third method— viz. moulding. As a large proportion of the candles consumed in the present day are composed of stearin or paraffin, or mixtures of these, the production of these substances therefore deserves most attention. Paraffin candles are most largely used in the United Kingdom, but on the Continent stearin candles are preferred.
Stearin.—This is the trade name for stearic and palmitic acids and mixtures thereof. Previous to the classical researches of Chevreul (1811-25) oils and fats were regarded as simple organic substances, but he proved them to be compound bodies. The neutral fats as they occur in nature are mixtures in variable proportions of the solids stearin or palmitin, and the liquid olein. Thus, fresh tallow consists of a mixture of stearin and olein, and neutral palm-oil of palmitin and olein. These bodies are known to chemists as glycerides or saponifiable fats—that is to say, when heated with an alkali, alkaline earth, or metallic oxide, in the presence of water, soap is formed, and glycerin is set free. When an alkali is used, the soap is soluble in water; but when an alkaline earth—e.g. lime—is employed, an insoluble soap is formed. When the soap is decomposed by the action of sulphuric acid, the fatty acids are liberated, and an insoluble sulphate of lime produced. Thus, from olein are obtained glycerin and oleic acid; from stearin, glycerin and stearic acid; and from palmitin, glycerin and palmitic acid. Chevreul, in conjunction with Gay-Lussac, began the industrial attempt of applying the scientific principles he had discovered, but he was unsuccessful, and it was left to another Frenchman, M. de Milly, to lay the foundation of the stearic acid industry in 1832. The researches of Messrs G. Wilson and Jones in 1842-43, which showed how dark fats could be converted into white fatty acids, gave a great impetus to the manufacture. Up to the time of the introduction of Messrs Wilson and Jones' acidification method, only tallow of good colour was available for conversion into fatty acids.
The process in most general use for converting fats into glycerin and fatty acids (distilled stearin) is briefly as follows: A mixture of palm-oil and tallow is digested in a copper vessel, called an 'autoclave,' with water and a small quantity (about per cent.) of lime under a pressure of eight atmospheres, and the result is the production of a dilute solution of glycerin ('sweet water') and a mixture of palmitic, stearic, and oleic acids, partly in combination with the lime used as the decomposing agent. The contents of the autoclave are transferred to a tank whence the 'sweet water' is drawn off, and the lime is then separated from the fatty acids by means of sulphuric acid. The fatty acids, which are dark in colour, are now treated with sulphuric acid at a high temperature, and subsequently well boiled with water, and then distilled. The distillate is of a good white colour, and may be used for composite or snuffless dip candles. The next stage in the process is the separation by hydraulic pressure, cold and hot, of the liquid oleic acid from the solid fatty acids. The oleic acid (technically 'olein') is used chiefly by wool-workers for oiling the wool. The solid fatty acids (technically 'stearin') is now ready for the candlemaker. The process here described is employed for the manufacture of what is known in the trade as 'distilled stearin'; but a harder and more expensive material, known as 'saponified stearin,' is prepared from tallow of good colour by saponification and hydraulic pressure, but without acidification or distillation.
Paraffin.—This substance was practically unknown to the candlemaker until 1847-50, when the late Dr James Young discovered the method of producing hydrocarbons by the distillation of coal at a low red heat. It is now produced in Scotland from shale in large quantities, in the United States from petroleum, in Germany, in smaller quantities, from brown coal, and in Burma, in yet smaller quantities, from Rangoon petroleum. Crude paraffin (technically 'scale') contains, in addition to the harder paraffins suitable for candles, soft paraffin (used by match-makers), and a small proportion of oil. The refining of paraffin is a very simple matter, and is now generally carried on in the way introduced into the works of Price's Patent Candle Company, by the inventor, Mr Hodges. The scale is melted and cast into thin cakes, which are then placed on sloping shelves in an oven kept at a regulated temperature sufficiently high to melt the soft paraffin. The soft paraffin and oil flow away, and leave behind a mass of hard paraffin, which, after a treatment with ivory or other black, is ready for the candlemaker.
Candle Moulding.—Before describing the manner in which stearin, paraffin, and other candles are moulded, the wicks need attention. Previous to the introduction of plaited wick almost all candles needed to be snuffed from time to time—that is to say, the imperfectly consumed wick standing in the midst of the flame had to be removed by snuffers, a necessary domestic instrument resembling a pair of scissors with a small box attached to one of the limbs. With the plaited wick (which was introduced in France in 1825 by Cambacères) snuffing is not required, for during combustion the wick bends over, so that the heated extremity receives a supply of oxygen, and is completely consumed. Before being used the wick is steeped in a solution of borax and sulphate of ammonia, and afterwards thoroughly dried, the object of this chemical preparation being to allow of the regular removal during combustion of the ash of the wick in minute glassy particles. But for this treatment the ash would remain to impede the capillary action of the wick.
The modern candle-moulding machine is the result of the labours of several inventors, both English and American. It may be described as an oblong cast-iron box, a little deeper than the length of the candles, supported and fixed to frames at each end. On the top of the box, and partly within it, are fixed two cast-iron dishes or troughs; at the bottom of these troughs, and also at the bottom of the box, are drilled holes to receive the candle-moulds, to which they are securely and accurately fitted so as to be quite watertight. Under the box is an iron plate, called the rising table, having holes coinciding with the holes in the box; this is actuated by a rack and pinion or wheel fixed to the frames so that the table can be raised or lowered at pleasure. Under the table is fixed a box to hold the bobbins on which the wick is wound, one bobbin for each mould.
The moulds may be described as tapered tubes, one end being contracted inside so that a nut may be screwed thereon; the part of the mould in which the tip of the candle is cast or moulded is made separate from the body of the mould, but it is accurately fitted to the bottom part of the mould so that no hot candle material can leak past it; this tip is fixed to one end of an iron tube, the other end of the tube being fixed to the iron table, so that when the table is raised or lowered the tips are raised and lowered also; the tips thus become a plunger to force the candles out of the moulds. There is a small hole through each tip just large enough to admit the cotton wick, and when the table is lowered the wicks are pulled down so as to be straight and central in the moulds. To complete the machine it is necessary to have two movable clamps to hold one set of candles while another set is being moulded. It is necessary also to attach a steam and water pipe to the east-iron box so as to warm or cool the moulds. The candle is cast downwards, the top of the candle being at the bottom of the mould.
The bobbin-box having been filled with the bobbins upon which is wound the properly prepared wick, one end of each wick is pulled through the tubes and little holes in the tips by means of an elongated crochet-hook, the table is lowered and the moulds brought to a proper temperature by the surrounding water that had been warmed by turning on the steam for a short time. The candle material in a melted state is then poured into the dishes or troughs, so filling the moulds and partly filling the troughs—the material in the troughs being needed to make up for the contraction while cooling. As soon as the moulds are full, cold water is turned into the box in order to cool the candles speedily; and when they are sufficiently cooled, the superfluous material is scraped out of the troughs. The table is now raised, forcing the candles out of the moulds and into the clamps which had been placed on the machine to receive them. The clamps are then closed, thus holding the candles over the moulds, and the tips are withdrawn by lowering the table, leaving the candle-machine ready for a second lot of candles.
The production in the United Kingdom of paraffin, stearin, and composite candles is estimated to be about 36,000 tons per annum. The largest candlemaking establishment in the world is that of Price's Patent Candle Company, whose works are situated near London and Birkenhead.
Corpse candles are candles used at the watching of a corpse before interment, and the name is given also to Will-o'-the-wisp, as portending death. For candles in public worship, see LIGHTS (USE OF).