The melting of the mass should be conducted at the lowest possible temperature, sufficing only to keep it in a fluid state. Quantities of 20 lb. to 25 lb. are treated at a time in a vessel large enough to permit quick stirring. Often the furnace used resembles an ordinary cook stove, the fire heating cast-iron plates; but these are objectionable from the inequality of the heating, and the risk of fire. Brannt describes an improved form of melter which serves also for the polishing. It consists of a small furnace about 3 ft. 3 in. high, fed preferably with small coke, having an upper and lower door for regulating the draught, but ho grate, the ashes being withdrawn at the lower door. The stove is completely enveloped in a sheet-iron casing at a distance of about 2 in., and at the same height above the floor. The air between the stove and the casing becomes hot, and as it passes away it is replaced by a cold current entering at the 2-in. opening between the casing and the floor. Beside the casing of the stove, and connected with it, stands a table, surrounded by a sheet-iron screen, and bearing a sheet-iron tub filled with sand and provided with iron supports.
The tub is covered with a plate of sheet-iron (for catching stray drops of wax), having 4 or 6 holes, which contain the melting pots. The hot air arising from the stove heats the sand tub and its contents, till the sealing-wax in the pots begins to melt. As soon as it melts, the fire is slackened by closing the lower door, as the heat retained by the sand suffices for a long time to keep the mass in a fluid state. Enamelled .cast-iron pots are best for melting in, keeping a separate pot for each mixture. Before using a pot for a new colour, it must be allowed to get quite cold, when the adhering wax can be easily cleaned off. The shellac is first put into the pot and melted, while being continually stirred with a flat paddle of hard wood, the turpentine is then intimately incorporated: next follow the neutral bodies and colours in a thin stream, with constant stirring, which is more necessary if the pigments are heavy When the mass seems uniform, drops of it are examined by letting them fall on a cold, smooth, metallic plate, when the colour, hardness, and fracture can be tested.
When satisfactory, the heat is adjusted to maintain a fluid condition, aromatic substances are quickly stirred in, and "forming " is commenced.
Sealing-wax is moulded into sticks in special "forms,'1 consisting of one piece for rectangular or triangular sticks, but must be of two for oval or round. Forms in one piece are made of rectangular brass plate, carrying grooves 1/25 in. wider at top than at bottom, for facilitating removal of the sticks. It is a common practice to put forms on a stove, or cool them off while moulding by placing them on metallic trays with cold water beneath, to cool the sticks rapidly; this releases the forms more quickly, but makes the sticks brittle, and it is better to let them cool gradually on a wooden table, while if the form becomes so warm as to much protract the setting of the wax, it may be dipped in cold water and carefully dried before using again. Engraved forms are difficult to turn out, but this may be partly remedied by slightly rubbing the engraved parts with oil of turpentine. Surface ornamentation, as gilding or silvering, is effected by placing the substance in the form. As brass forms are expensive, they are sometimes replaced by home-made ones of type-metal. To produce them, a stick of fine wax is coated with a thin film of olive oil, and a cast of it is taken in plaster-of-Paris; when this is thoroughly dry, it is put into a small wooden box, and melted type-metal is poured round to make a form.
The forming of the wax is conducted as follows. The molten wax is ladled from the pot into a casting spoon, previously heated. By this it is poured in a uniform stream into the forms. These should be slightly warmed before the first moulding takes place.
Polishing, dressing, or enamelling is usually applied to all grades, though the finer qualities have a lustrous surface on coming out of the form. When the improved furnace before mentioned is not in use, a special polishing stove is necessary. This consists of an iron slab covering a vault, heated by a fire beneath. The sticks are taken in the hand and held in the heat of the polishing stove till the surfaces begin to melt and the sticks bend. When thus softened, they receive an imprint of the maker's name or some other device, composed of letters held in a little brass hand frame. The sticks are patted between small wooden boards at the same time, to retain their shape.
For gilding, silvering, or bronzing, the part to be ornamented is touched with a brush dipped in strong spirits of wine, and the gold or silver leaf, or bronze powder is applied, and adheres tenaciously.
The following recipes for the compounding of sealing-waxes will be found to embrace all that are of general utility.
(2) 8 parts shellac, 6 turpentine, 6 resin, l 1/2 chalk, 1 gypsum, 3 1/2 vine-black.
(3) 48 parts shellac, 52 turpentine, 46 pine resin, 28 chalk, 8 soot, 8 bone-black, 8 asphaltum.
(1) 7 parts shellac, 6 turpentine, 3 1/2 pine resin, 1 magnesia, 2 chalk, 2 to 2 1/2 blue colouring matter. (2) Light-blue sealing-wax is produced by mixing Berlin blue with oxide of zinc or nitrate of bismuth, and has a beautiful enamellike appearance. As blue colours are very sensitive, bleached shellac should always be used, and care must be exercised in the choice of the rosin, that which is opaque and brown-coloured' being rejected.
The most ordinary sorts of sealing-wax are used for bottles, and of course can only be coloured with the cheapest kinds of tinctorial matter. Many makers prepare bottle-wax of a mixture of common pine resin, turpentine, chalk, and the respective colouring matter only. Such are very cheap, but they do not answer the purpose so well as they should. The corks are covered with a layer of sealing-wax by dipping the necks of the bottles into the melted mass. This congeals very quickly on the cold glass, and consequently at once becomes brittle, and frequently breaks when gently touched. On trying to make the wax less brittle by increasing the turpentine, it often happens that it remains sticky even in cold weather. To avoid these evils, add a certain quantity of shellac, 10 to 15 per cent., to the composition. This will increase the cost of the article somewhat, but its quality will be so much improved, that it will not become sticky even in a hot climate.