This is done by wick-mordants, by means of which they are rendered less combustible, especially those for stearine and composite candles. Compounds composed of solutions of ammoniac salts, of bismuth, of borates, or boracic acid, are used. A simple and cheap mordant for wicks is a sal ammoniac solution of 2° to 3° B. This concentration is strong enough, and if a weaker one be used, a spark will remain on the wick after the candle has been blown out, and burning down to the fat, made relighting more difficult. Before moulding is performed, the wicks, having been saturated, are thoroughly, dried in a tin box, surrounded by a jacket, in which steam is introduced. Instead of the sal ammoniac, phosphate of ammonia is used in some factories. A very good mordant is also a solution of 2 4/10 oz. boracic acid in 10 lb., of water, with 1/3 oz. of strong alcohol, and a few drops of sulphuric acid. Some mordants have become unpopular; the fault is in the crude cotton, which does not always readily become moistened; consequently, from not having completely imbibed the mordant, portions of the thread remain unsaturated, and are not equally combustible with the others.
An admixture of alcohol will remedy this defect, as cotton is more easily moistened in dilute spirit than in pure water.
These candles are made by stringing a certain number of wicks upon a rod, and dipping them in melted tallow repeatedly. The process is very simple; the clarified and remelted tallow is poured into a tightly-joined walnut or cherry trough, 3 ft. long by 2 ft. wide, and 10 to 12 in. wide at the top, gradually diminishing to 3 or 4 in. at the bottom. A handle is fixed on each end for its easy removal, and when not in use it is closed with a cover. The operator commences by stringing 16 to 18 wicks at equal intervals on a thin wooden rod, about 2 1/2 ft. long, and sharpened at the ends. He then takes 10 or 12 such rods and dips the wicks rapidly into the fluid tallow in a vertical direction. The tallow should he very liquid, in order that the wicks be soaked as uniformly as possible, after which the several rods are rested on the ledges of the trough, when, if any of the wicks be matted together, they are separated, and the rods so placed on a frame, having several cross-pieces, that the uncongealed tallow from the wicks may drop down, and while this is going on, which continues till the tallow is cooled and solidified, the operator is engaged in preparing another batch of rods.
The fat in the trough, meanwhile, is so far cooled that in immersing the first dip again a thicker layer will adhere to the wicks. It is considered that when the tallow solidities at the sides of the vessel, the temperature is the most convenient for the object in view. It is sometimes necessary to stir the ingredients to produce a uniform admixture, and in such cases much care should be taken so that no settlings be mingled with the mass, whilst by the addition of hot tallow any desired temperature may be obtained. The tallow on the wicks after each dipping becomes so gradually hardened, that at the third or fourth immersion new layers necessarily solidify; as a natural consequence, of the method of dipping, the lower ends of the wicks become thicker than the upper, to remedy which the lower ends are again put into the melted fat for a few minutes, when the heat, as a matter of course, diminishes their dimensions. The process of dipping is continued until the candles acquire the requisite thickness.
The conical spire at the upper end is formed by immersing deeper at the last dip, and if, eventually, the candles are too thick at the lower end, they are held over a slightly-heated folded copper sheet, so that the fat may melt, but not be wasted.
For moulding, common metal moulds, a mixture of tin and lead, are used. They are slightly tapering tubes, varying in length and dimensions according to the size of the candle to be manufactured, and, when required, are arranged in regularly-perforated wooden frames or stands, with the smaller end downwards, forming the upper or pointed part of the candle. At this smaller end, the wick, previously saturated in melted fat, is inserted, filling the aperture, and, passing up the centre, is fastened perpendicularly at the upper end of the tube, to which is attached a movable cover. The melted fat is then poured in, generally with a small can, but a tinned iron siphon is better. It is requisite that the tallow should completely fill the mould, that it should remain uncracked on cooling, and should be easily removable from the moulds. This can, however, only be obtained when the fat at the sides cools more quickly than that, in the interior, and when the whole candle is rapidly cooled. A cool season is, for this reason, far better; but a certain condition of the tallow, namely, that which it possesses at a temperature very near its melting point, is absolutely necessary.
Candle-makers recognise the proper consistence of the tallow for moulding by the appearance of a scum upon the surface, which forms in hot weather between 111° and 119° F., in mile weather at 108° F., and in cold about 104° F. The tallow is usually melted by itself, sometimes, however, over a solution of alum. The candles are most easily removed from the mould the day after casting, to be cut and trimmed at the base. Moulding by hand is a very tedious operation, and only practised in the smaller factories; in more extensive establishments, where economy of time and labour is a consideration, machinery is employed.
Melt together, over a water bath, 100 parts of stearic acid, and 10 to 11 parts of bleached beeswax; but, to ensure success, the mixture must remain over the bath from 20 to 30 minutes, without being stirred or agitated. At the end of that time the fire is to be extinguished, and the fluid allowed to cool until a slight pellicle is formed on the surface, when it is cast direct into the moulds, previously heated to the same temperature, with the precaution of avoiding stirring the mixture, which would cause opaqueness.
For 100 lb. of stock take 90 lb. of spermaceti, 5 lb. purified mutton suet, and 5 lb. wax; melt each separately over a water bath, and to the whole, when mixed together, add 2 oz. of alum and 2 oz. of bitartrate of potash in fine powder; and, while stirring constantly, raise the heat to 176° F.; then withdraw the fire and allow the mixture to cool to the temperature of 140° F. When the impurities subside, the clear liquid must be drawn off into clean pans. Paraffin wax is an excellent substitute, and much less costly. For quality and good appearance, candles made of this cooled block are more than proportional to its cost. Substitute plaited wicks for the foregoing mixture to the wicks generally used for composite candles, and prepare them by previously soaking in a solution of 4 oz. borax, 1 oz. chlorate of potash, 1 oz. nitrate of potash, and 1 oz. sal ammoniac, in 3 quarts of water. After being thoroughly dried, they are ready for moulding.
It is made by melting together, in a steam-jacket,2 1/2 to 17 1/2 lb. of vegetable wax, 1 1/2 to 10 1/2 of pressed mutton tallow, and 22 to 46 lb. of stearic acid. The latter and the vegetable wax are the hardening ingredients. By changing the proportions between the above limits, a more or less consistent mixture may be formed. The moulding is performed in the same manner as for stearic-acid candles.
The great objection to tallow candles is the frequent necessity for removing the snuff, or charred wick, which rises into the body of the flame and obscures the light. If the wick can be exposed to the air it will be entirely consumed, (a) This is done in composite candles by plaiting the cotton into a flat wick, which as it burns curves over. Sometimes a very fine wire is included in the wick, which is usually dipped in a solution of borax.
(b) Twist the wick with one strand shorter than the others, which will bend the wick slightly when the fat melts.
For a more detailed account of candle making on the industrial scale, see Spons' Encyclopaedia.