To Soften and Restore India Rubber Hose, etc.—I. Dip in petroleum and hang up for a couple of days. Repeat process if necessary.
II. The above process is applicable to all articles, but is specified for hose. It is stated that old rubber that has become hard may be softened by exposure first to vapor of carbon disulphide, followed by exposure to the vapor of kerosene. The latter vapor is found to be a general preservative for india rubber.
III. Dr. Pol recommends immersion in a solution of water of ammonia, 1 part, and water 2 parts, from a few minutes to an hour.
To Prevent Decay of Rubber Tubing.—The decay of rubber tubing has been attributed to the formation of sulphuric acid from the sulphur mixed with it. M. Ballard has suggested washing with water or weak alkaline solution five or six times in a year.
Joints between India Rubber Tubing and Metal.—Where tubing is temporarily slipped over metal gas pipes and similar connections, as in the chemical laboratory, it is well to apply glycerine to the metal. It acts as a lubricant in slipping the tubing on, and assists in its withdrawal.
Preserving Vulcanite.—Wash occasionally with a solution of ammonia and rub with a rag slightly moistened with kerosene oil.
Effect of Copper upon Rubber.—In a paper read before the recent meeting of the British Association, Sir William Thomson stated that metallic copper, when heated to the temperature of boiling water, in contact with the rubber, exerted a destructive effect upon it. With a view to finding whether this was due to the copper per se, or to its power of conducting heat more rapidly to the rubber, he laid a sheet of rubber on a plate of glass, and on it placed four clean disks, one of copper, one of platinum, one of zinc and one of silver. After a few days in an incubator at 150° F., the rubber under the copper had become quite hard, that under the platinum had become slightly affected and hardened at different parts, while the rubber under the silver and under the zinc was quite hard and elastic. This would warrant the inference that the metallic copper had exerted a great oxidizing effect on the rubber, the platinum had exerted a slight effect, while the zinc and silver respectively had no injurious influence on it. The rubber thus hardened by the copper contained, strange enough, no appreciable trace of copper; the copper, therefore, presumably sets up the oxidizing action in the rubber without itself permeating it.
Gas Tight Tubings.—Fletcher has invented a gas tight rubber tubing in which a layer of tinfoil is interposed between two concentric rubber tubes, all vulcanized together.
Printing Colors upon India Rubber.—It may sometimes be desirable to have a surface of vulcanized india rubber so prepared that it will take colors such as are used for calico printing. This end is simply attained by sprinkling the article with farina before vulcanizing. A small quantity attaches itself and forms an excellent base for color printing.
Gutta-Percha for Coating Glass.—For focusing glass in photography and for similar purposes where ground glass or a translucent material is required, a solution of gutta-percha in chloroform is highly recommended. This is flowed over or painted on the glass and is allowed to evaporate afterwards.
Burned Rubber.—A very soft pure gum sold for artists’ use is improperly termed burned rubber. It is used in crayon work for removing and lightening marks by dabbing it against the paper, cleaning the rubber from time to time. It is so soft that it picks up and removes crayon marks without the necessity of friction. Thus the rubbing out or more properly erasing operation can be localized and crayon tints can be lightened in tone without impairment or “smutting.” It is a very elegant accessory to the artists’ paraphernalia. To make it, pure virgin gum, preferably the best Para, is cut into pieces and soaked for some hours in benzole. A long soaking is advisable. The pieces are then removed from the benzole and are ground in a mortar until perfectly homogeneous. The mass is gathered up with a spatula and is pressed into little tin boxes. If desired it may be dried upon a water bath. This is not necessary as, if the box is left open, it will rapidly season itself. It should be very soft, should tend to adhere to the fingers, yet should leave them easily, and should strip cleanly from the box. A very little turpentine makes it more adhesive. It may even be softened in turpentine alone. This gives a gum that seasons more slowly and is in some respects preferable to the benzole made preparation. It is sold at a high price by the dealers, as the demand for it is limited.
Rubber Sponge.—This is also an artist’s rubber. It is also used for cleaning kid gloves. It is made by incorporating with the masticated or washed and sheeted gum any material or materials that will give off vapor in the curing process. Damp sawdust and crystallized alum are used as giving off vapor of water or steam, or ammonium carbonate as giving off vapors of ammonia carbonic acid gas and steam. The mixed gum may be cured in moulds, which it will fill by its expansion.
Shellac Varnish for India Rubber.—This is made by soaking powdered shellac in ten times its weight of strong aqua ammonia (26° B.). At first no change beyond a coloring of the solution is perceptible. After many days standing the bottle, which should have a glass stopper, being tightly closed, the shellac disappears, having entered into solution. It may be a month before complete solution. This forms an excellent varnish for india rubber shoes and similar articles. It may be applied with a rag. It is also a good application for leather in some cases and doubtless many other uses could be made of it. It would act well as a vehicle for a dark pigment such as lamp-black. It will rejuvenate a pair of india rubbers very nicely. The ammonia exercises also a good influence on the rubber. It has been recommended as a cement for attaching rubber to metal, but its adhesive powers are not always satisfactory.
Simple Substitute for Stamps.—A very simple though rough and imperfect substitute may be made by gluing with common carpenter’s glue pieces of thick string upon a piece of wood, the string being given the form of the desired letters. Care must be taken to avoid saturating and stiffening the string with the glue.
India Rubber Substitutes.—One of these under the name of vulcanized oil is thus described by Bolas:
“Vulcanized oil is, perhaps, of more interest, and many oils, such as linseed and others resembling it, may be vulcanized by being heated for some time to 150° Centigrade with twelve to twenty per cent. of sulphur. The product obtained is soft, and somewhat resembles very bad india rubber. By increasing the proportion of sulphur very much indeed, say to four times the weight of the oil, and vulcanizing at a higher temperature, a hard substance, resembling inferior vulcanite, is obtained.
“Soft and hard vulcanized oil have been introduced into commerce at various times and under many names; but these materials never seem to have made very much headway.”
Another method of treating the oil consists in mixing it with a solution of chloride of sulphur in carbon disulphide or in naptha. On standing, the volatile solvents escape, leaving a thick mass, which is the substitute.
In combinations of aluminum with the fatty acids, forming aluminum soaps, and of these, aluminum palmitate especially, a substitute for india rubber has been sought but without success.
Metallized Caoutchouc.—Unvulcanized gum is mixed with powdered lead, zinc, or antimony. The mixed india rubber is then cured as in the regular process.
Bolas thus describes their manufacture:
“When ordinary vulcanized rubber is heated to 230° Centigrade, (446° F.) or until it melts, a permanently viscous product is obtained, and this substance, if mixed with emery and sulphur to a kind of paste, forms a material out of which the so-called agglomerated emery wheels or grinders may be formed, the mixed materials being next hardened or cured by the application of a steam heat. Emery wheels and hones made on this principle were introduced by Deplanque about twenty-three years ago.
“Thirty-five parts of old vulcanized caoutchouc having been placed in a kind of still, heat is applied to melt it, the operation being assisted by the gradual addition of about ten parts of heavy coal oil; but this latter is afterward distilled off. The softened caoutchouc is then incorporated with 500 parts of emery of the required degree of fineness and nine parts of sulphur. These materials having been thoroughly mixed, the hones or wheels are manufactured, and afterward cured or baked at a heat of 140° Centigrade, (284° F.) during a period of about eight hours. Grinding wheels, made in the above manner, can be worked at a speed of 2,000 revolutions per minute, and are extremely useful for the working of hardened steel or other obdurate materials.”
Etching on Metals and Glass.—India rubber stamps can be used for placing the ground upon knife blades and similar articles which are to be etched. The parts untouched by the stamp are attacked by the acid. In the case of glass, diamond ink (page 133) can be put on with a stamp. The acids for metal etching might be thickened with barium sulphate also and applied in the same way. In these cases the inscription of the stamp would be etched. Where ground is put on, whether on glass or metal, the design for the stamp will be protected.
Etching Ground for Metals.—Equal parts of asphalt, Burgundy pitch and beeswax melted together and mixed thoroughly. It may be softened with mutton suet. Beeswax may be used, dissolved in ether or simply melted. Yellow soap is sufficient for ordinary work.
Etching Solutions for Biting in.—For steel and iron, a. sulphate of copper and common salt in solution. b. sulphate of copper, sulphate of alumina, and common salt, of each two drachms; acetic acid, 1½ oz. c. sulphuric acid, diluted with five volumes of water with a little sulphate of copper. For other metals, except gold and platinum, nitric acid diluted with five volumes of water.
Etching Ground for Glass.—Melted beeswax is generally recommended. It can be removed with spirits of turpentine after as much as possible has been scraped off.
Etching Glass.—Glass may be conveniently etched by exposing it to the vapor of hydrofluoric acid. A shallow leaden tray, as large as the glass, is required. A quantity of fluorspar is placed in it and is moistened with concentrated sulphuric acid. The glass is placed face downward over the tray. It is supported over the mixture by resting on the edges of the tray or by any simple method, and the whole is covered with a towel. In half an hour or more the etching will be completed. The vapors must not be allowed to escape into any room containing glass or metal articles as they corrode everything. Great care should be taken also not to let the mixture touch the hand, as painful ulcers are the result.
India Rubber Shoe Blacking.—Raw india rubber is given as a constituent of several shoe blackings. Formulæ are given as below for paste and liquid blackings.
I. Paste blacking: bone-black, 20 parts; molasses, 15 parts; vinegar, 4 parts; sulphuric acid, 4 parts; caoutchouc oil (as given below), 3 parts.
II. Liquid blacking: bone-black, 60 parts; molasses, 45 parts; gum arabic dissolved in water, 1 part; vinegar, 50 parts; sulphuric acid, 24 parts; caoutchouc oil, 9 parts.
Caoutchouc oil is made by dissolving or digesting virgin rubber 55 parts in linseed oil 450 parts.
Waterproof Composition for Boots.—One ounce of virgin rubber cut into pieces is digested in enough oil of turpentine to form a stiff paste. In applying heat take great care lest the contents of the vessel become ignited. When homogeneous, which condition may be brought about by rubbing in a porcelain mortar, as described in chapter XII., it is mixed with 5–6 ounces of boiled linseed oil. This gives an ointment almost of the consistency of butter.