Appliances and Apparatus used in Japanning and Enamelling.

Besides the various enamels or japans and varnishes of various colourings and the stove, which will be found described and illustrated, together with the trough, in other pages, the worker will need some iron pots or cauldrons in which to boil the potash "lye" for the cleansing, more particularly, of old work, some iron ladles both for this work and for pouring the japan on the articles to be covered therewith, a few badger tools and brushes for small fine work, some hooks for the stove, a pair of pliers, a few bits of broom handle cut into short lengths and made taper, so as to fit into the tubes, etc., of bicycles and other work, so as to keep the hands as free from the japan as possible, some emery powder, pumice-stone powder, tripoli, putty powder, whiting, and a piece of felt or cloth. If he is also doing any common work, a stumpy brush of bristles and a soft leather will also be requisite, together with a file or two. These will about comprise the whole of the articles required, not very expensive, all of which will really not be required by a beginner.

Owing largely to the strides made in the cycle trade enamelling is stoved by means of gas, and of this a plentiful supply is necessary. Enamelling stoves may really be described as hot-air cupboards or ovens, and for a stove which will answer most requirements—say one of 6 feet by 6 feet by 31/2 feet—six rows of atmospheric burners will be necessary to heat it, while it will be also advisable to fix pipes of 11/4 inch internal diameter from the gas meter to the stove. The atmospheric burners can be made from the requisite number of pieces of 11/4-inch gas tube 31/2 feet in length, one end of each being stopped, and having 1/3-inch holes drilled therein at intervals of about 1 inch, the other end being left open for the insertion of ordinary 3/8-inch brass gas taps. Another plan preferred by some japanners is to have three rows of burners the full length of the stove, which, under some circumstances, due to structural conditions, will be found more suitable. Anyway, whatever the position of the stove, allowance must be made for a temperature up to 400° F. to be raised. In old-fashioned ovens the heat is applied by means of external flues, in which hot air or steam is circulated, but this system is generally unsatisfactory, the supply of heat having to be controlled by dampers or stop-cocks, and this has given place to the gas apparatus. Another simple form of oven, though not one which I shall recommend, is a species of sheet-iron box, which is encased by another and larger box of the same shape, so placed that from 2 to 3 inches of interspace exists between the two boxes. To this interspace heat is applied, and a flue will have to be affixed to this apparatus to carry off the vapours which arise from the enamel or japan. For amateur or intermittent jobbing work the oven illustrated in Figs. 2 and 3 is about as good as any, though to guard against fire it would be as well to have a course of brickwork beneath the oven, while if this is not possible on account of want of height, a sheet or so of zinc or iron will help to mitigate the danger. It is also advisable, if the apartment is a low-pitched one, to have a sheet of iron or zinc suspended by four corner chains from the ceiling in order to protect this from firing through the heat from the enamelling oven. Of course, it will be understood that every portion of the stove must be put together with rivets, no soldered work being permissible.

Fig. 2.—Door of Oven when Shut.
Fig. 2.—Door of Oven when Shut.

To those who wish to construct their own stove, it will be found that the framework can be shaped out of 1-inch angle iron, the panels or walls being constructed of sheet-iron of about 18 gauge, the whole being riveted together. The front will be occupied in its entire space by a door, which will require to be hung on strong iron hinges, and the framework of this door should be constructed of 1 inch by 1/4 inch iron—a rather stouter material will really be no disadvantage—to which the sheet-iron plates must be riveted. In the centre of the door must be cut a slit, say 11/2 inches by 9 inches, which will require to be covered with mica or talc behind which must be placed the thermometer, so as it can be seen during the process of stoving, without the necessity of opening the door, which, of course, more or less cools the oven. And, by the way, this thermometer must register higher than the highest temperature the oven is capable of reaching. Above is shown a sketch of the stove, interior and exterior, which will give an idea of what a japanner's stove is like.

Fig. 3—Showing Stove when Open, and Back of Door. 
Fig. 3—Showing Stove when Open, and Back of Door.

Inside the stove it will be necessary to fix rows of iron rods, some four inches from the top, from which to suspend the work, or angle-iron ledges can be used on which the rods or bars can be fixed, these arrangements being varied according to the particular description of work, individual fancy, or other circumstances. Large S hooks are about the handiest to use. A necessary adjunct of the stove is a pan, which can be made by any handy man or tinworker, which should be made to fit the bottom of the stove above the gas jets, it being arranged that it rests on two side ledges, or along some rods. One a couple of inches in depth will be found sufficient, and it will repay its cost in the saving of enamel, it being possible with its use to enamel a bicycle with as little as a gallon of enamel. Some workmen have the tray made with a couple of hinged side flaps, to turn over and cover up the pan when not in use, but this is a matter of fancy. Of course, they must always be covered up when not in use. For those who would prefer to use Bunsen burners, I show at Fig. 4 a sketch of the best to employ, these having three rows of holes in each.

Fig. 4.—Bunsen Burner.
Fig. 4.—Bunsen Burner.

When brick ovens are employed they must be lined with sheet-iron, and in these very rare circumstances where gas is not available, the stove can be heated with coal or wood, which will, of course, involve a total alteration in the structural arrangements. I have not given the details here, as I do not think the necessity will ever arise for their use, and for the same reason I have refrained from giving the particulars for heating by steam and electricity, or the other methods which have been adopted by various workers, as there is no question but that a gas stove or oven, as described, is about the best and handiest for jobbers or amateurs.

Modern Japanning and Enamelling Stoves.

The modern japanning and enamelling stove consists of a compartment capable of being heated to any desired temperature, say 100° to 400° F., and at the same time, except as regards ventilation, capable of being hermetically sealed so as to prevent access of dust, soot, and dirt of all kinds to mar the beauty and lustre of the object being enamelled or japanned. Such a stove may be heated—

1. By a direct coal, coke, wood, peat, or gas fire (which surrounds the inner isolated chamber) (Fig. 5).

2. By heated air.

3. By steam or hot-water pipes, coils of which circulate round the interior of the stove or under the floor.

Such ovens may be either permanent, that is, built into masonry, or portable.

Fig. 5.—Greuzburg's Japanning Oven.
Fig. 5.—Greuzburg's Japanning Oven.

1. Stoves heated by direct fire.—These were, of course, the form in which japanning ovens were constructed somewhat after the style of a drying kiln. Fig. 5, Greuzburg's japanning oven heated on the outside by hot gases from furnace. The oven is built into brickwork, and the hot gases circulate in the flues between the brickwork and the oven, and its erection and the arrangement of the heating flues are a bricklayer's job. Coke containing much sulphur is objectionable as a fuel for enamel stoves Mr. Dickson emphasizes this very forcibly. He says: "In the days when stoves were heated by coke furnaces, and the heat distributed by the flues, the principal trouble was the escape of fumes of sulphur which caused dire disaster to all the enamels by entering into their composition and preventing their ever drying, not to speak of hardening. I have known enamels to be in the stoves with heat to 270° for two and three days, and then be soft. The sulphur also caused the enamels to crack in a peculiar manner, much like a crocodile skin, and work so affected could never be made satisfactory, for here again we come back to the first principle, that if the foundation be not good, the superstructure can never be permanent. The enamels, being permeated with sulphur and other products from the coke, could never be made satisfactory, and the only way was to clean it all off. The other principal troubles are the blowing of the work in air bubbles, which is caused mainly by the heat being too suddenly applied to the articles, but these are very small matters to the experienced craftsman."

Fig. 6.
Fig. 6.

2. Stoves heated by hot-water pipes.—Let us first of all consider the principle on which these are constructed. In Perkins' apparatus for conveying heat through buildings by the circulation of water in small-bore hot-water pipes an endless tube or pipe is employed, the surface of which is occasionally increased by spiral or other turnings where the heat is to be given off or acquired: the annexed figure may serve to illustrate this principle; it represents a strong wrought-iron tube of about one inch diameter completely filled with water; the spiral A passes through a furnace where it is highly heated, and the water is consequently put into motion in the direction of the arrows; the boiling of the water or formation of steam is prevented by the pressure, whence the necessity of the extreme perfection and strength of the tube. B represents a second coil which is supposed to be in an apartment where the heat is to be given out. C is a screw stopper by which the water may be occasionally replenished. By this form of apparatus the water may be heated to 300° or 400°, or even higher, so as occasionally to singe paper. A larger tube and lower temperature are, however, generally preferable.[1]

Fig. 7.—Enamelling Stove—in a Tin-plate Printing Factory—heated by Perkins' Hot-water Pipes.
Fig. 7.—Enamelling Stove—in a Tin-plate Printing Factory—heated by Perkins' Hot-water Pipes.

The principle of Perkins' invention has, during the last eighty years, i.e. since the date of the invention in 1831, been very extensively applied not only for the heating of buildings of every description, but it has also been utilized for numerous industrial purposes which require an atmosphere heated up to 600° F. The principle lends itself specially to the design of apparatus for raising and maintaining heat evenly and uniformly, and also very economically for such purposes as enamelling, japanning, and lacquering.

The distinctive feature of this apparatus when applied to moderate temperatures lies in the adoption of a closed system of piping of small bore, a certain portion of which is wound into a coil and placed in a furnace situated in any convenient position outside the drying chamber or hot closet. The circulation is thus hermetically sealed and so proportioned that while a much higher temperature can be attained than is possible with a system of pipes open to the atmosphere, yet a certain and perfectly safe maximum cannot by any possibility be exceeded.

The efficiency of the apparatus increases within certain limits in proportion to the pressure employed, which fact explains the exceedingly economical results obtained, while the fact that, owing to the high temperature used, a small-bore pipe can be made more effective than the larger pipes used in any open system, accounts for the lower first cost of the Perkins' apparatus.

Fig. 8.—Japanning and Enamelling Oven Heated by Single Hot-water Pipes sealed at both ends with Furnace in Rear.
Fig. 8.—Japanning and Enamelling Oven Heated by Single Hot-water Pipes sealed at both ends with Furnace in Rear.
Fig. 9—Japanning and Enamelling Oven For Bedstead, Ironmongery, Cash-box, and Lamp Factories.
Fig. 9—Japanning and Enamelling Oven For Bedstead, Ironmongery, Cash-box, and Lamp Factories.
Fig. 10.—Japanning and Enamelling Stove for parts of Sewing Machines.
Fig. 10.—Japanning and Enamelling Stove for parts of Sewing Machines.

It will be seen from the various illustrations that the articles to be treated are absolutely isolated from actual contact with the fire or the fire gases and other impurities which must be an objection to all methods of heating by means which are not of a purely mechanical nature. This principle not only recommends itself as scientifically correct and suited to the purpose in view, but is also a very simple and practical one. It affords the means of applying the heat at the point where it is required to do the work without unduly heating parts where heat is unnecessary; it secures absolute uniformity, perfect continuity, and the highest possible fuel economy.

Fig. 11.—Japanning and Enamelling Stove for Iron-Bedsteads and Household Ironmongery with Truck on Rails.
Fig. 11.—Japanning and Enamelling Stove for Iron-Bedsteads and Household Ironmongery with Truck on Rails.
Fig. 12—Permanent Japanning and Enamelling Stove for Kitchen Utensils built in Masonry.
Fig. 12—Permanent Japanning and Enamelling Stove for Kitchen Utensils built in Masonry.

The nature of the work to be executed in the different classes and various sizes of stoves vary so greatly and indefinitely that only by careful attention to the special requirements of each case, on the part of the designers and constructors, is it possible to obtain the most satisfactory results.

The arrangement of fixing the pipes round the lower walls of the room in this form of stove is somewhat cumbersome, but in a roomy stove this slight drawback is not felt quite so much. However, it seems a good principle to leave every inch of internal space available for the goods to be enamelled or japanned, This principle is carried out to the letter in the other form of stoves described and illustrated in the sequel.

The figure shows a section through single chamber japanning and enamelling oven heated by hot-water pipes (steel) closed at both ends and partially filled with water which always remains sealed up therein, and never evaporates until the pipes require to be refilled.

This stove may be heated (1) by hot-water pipes (iron), (2) by super-heated water, (3) by steam, but only to 80° C. The different compartments may be heated to uniform or to different temperatures with hot water; the stoke-hole is at the side and thus quite separated from the stove proper.

The ovens must be on the ground floor, so that the super-heated steam from the basement may be available.

The great drawback to the use of gas for heating japanning and enamelling stoves is the great cost of coal gas.

Fig. 13.—Portable Gas Heated Japanning and Enamelling Stove fitted with Shelves, Thermometer, etc.
Fig. 13.—Portable Gas Heated Japanning and Enamelling Stove fitted with Shelves, Thermometer, etc.
Pigments Suitable for Japanning with Natural Lacquer.

White Pigments.—Barium sulphate and bismuth oxychloride. These two are used for the white lacquer or as a body for coloured lacquers. When the lacquer is to be dried at a high temperature barium sulphate is preferable, but when it is dried at an ordinary temperature bismuth oxychloride is better. Since the lacquer is originally of a brown colour the white lacquer is not pure white, but rather greyish or yellowish. Many white pigments, such as zinc oxide, zinc sulphide, calcium carbonate, barium carbonate, calcium sulphate, lead white, etc., turn brown to black, and no white lacquer can be obtained with them.

Red Pigments.—Vermilion and red oxide of iron. These two are used for the red lacquer, but vermilion should be stoved at a low temperature.

Blue Pigment.—Prussian blue.

Yellow Pigments.—Cadmium sulphide, lead chromate and orpiment.

Green Pigment.—Chromium oxide (? Guignet's green).

Black Pigment.—Lamp black. This is one of the pigments for black lacquer, but does not give a brilliant colour, therefore it is better to prepare the black lacquer by adding iron powder or some compound of iron to the lacquer.

Various mixed colours are obtained by mixing some of the above-mentioned pigments.

Examples of application are as follows:—

(1) Golden Yellow.—Finished lacquer, 10 parts; gamboge, 1 to 3; solvent, 5. If utensils are lacquered with this thin lacquer and dried for about 2 hours in an air-oven at a temperature of 120° C. a beautiful hard coating of golden colour is obtained.

(2) Black.—Black lacquer, 10 parts; solvent 2 to 4. Utensils lacquered with this lacquer are dried for about an hour at 130° to 140° C.

(3) Red.—Vermilion, 10 parts; finished lacquer, 4; solvent, 2. This lacquer is dried for about an hour at 130° to 140° C.

(4) Khaki or Dirty Yellow.—Barium sulphate, 100 parts; chromic oxide, 3; finished lacquer, 20 to 25; solvent, 15. This lacquer is dried for about half an hour at 160° C.

(5) Green.—Barium sulphate, 100 parts; chromic oxide, 20 to 50; finished lacquer, 40 to 50; solvent, 20. This is dried for about 10 minutes at 160° C.

(6) Yellow.—Barium sulphate, 100 parts; lead chromate, 40; finished lacquer, 40; solvent, 20. This is dried for about 15 minutes at 150° C.

Almost all pigments other than the above-mentioned are blackened by contact with lacquer or suspend its drying quality.

Several organic lakes can be used for coloured lacquers, that is to say, Indian yellow, thioflavin, and auramine lake for a yellow lacquer; fuchsine, rhodamine, and chloranisidin lake for a red; diamond sky blue, and patent nileblue lake for a blue; acid green, diamond green, brilliant milling green, vert-methyl lake, etc., for a green; methyl violet, acid violet, and magenta lake for a violet; phloxine lake for a pink. These lakes, however, are decomposed more or less on heating and fail to give proper colours when dried at a high temperature.

Modern Methods of Japanning and Enamelling with Natural Japanese Lacquer.

Urushiol, the principal constituent of Japanese lacquer, does not according to the Japanese investigator, Kisaburo Miryama, dry by itself at ordinary temperatures, but can be dried with ease at a temperature above 96° C. In the same way, lacquer that has been heated to a temperature above 70° C. and has entirely lost its drying quality can be easily dried at a high temperature. In this method of japanning the higher the temperature is, the more rapidly does the drying take place; for instance, a thin layer of urushiol, or lacquer, hardens within 5 hours at 100° C., within 30 minutes at 150° C., and within 10 minutes at 180° C. Japanning at a high temperature with natural lacquer does not require the presence of the enzymic nitrogenous matter in the lacquer, and gives a transparent coating which is quite hard and resistant to chemical and mechanical action; in these respects it is distinguished from that dried at an ordinary temperature. During the drying, oxygen is absorbed from the atmosphere and at the same time a partial decomposition takes place.

This method of japanning has its application in lacquering metal work, glass, porcelain, earthenware, canvas, papier-mâché, etc.; because the drying is affected in a short time, and the coating thus obtained is much more durable than the same obtained by the ordinary method.

For practical purposes it is better to thin the lacquer with turpentine oil or other solvent in order to facilitate the lacquering and lessen the drying time of the lacquer. Since the lacquer-coating turns brown at a high temperature, lacquers of a light colour should be dried at 120° to 150° C.; and even those of a deep colour must not be heated above 180° C. Most pigments are blackened by lacquer; therefore the varieties of coloured lacquers are very limited.

[1] A question has been raised concerning the safety of Perkins' apparatus, not merely as relates to the danger of explosion, but also respecting that of high temperature; and it has been asserted that the water may be so highly heated in the tubes as to endanger the charring and even inflammation of paper, wood, and other substances in their contact or vicinity: such no doubt might be the case in an apparatus expressly intended for such purposes, but in the apparatus as constructed by Perkins, with adequate dampers and safety valves, and used with common care, no such result can ensue. Paper bound round an iron tube is not affected till the temperature exceeds 400°; from 420° to 444° it becomes brown or slightly singed; sulphur does not inflame below 540°.