Rubber Stamps
A rubber stamp is type matter molded in rubber which is then mounted on a block with a handle as shown in [Fig. 77]. When the stamp is inked and then pressed on a smooth surface it leaves an impression on it.
Rubber stamps are useful for marking tags, books, boxes, bundles, etc., but it is very bad taste to use them for letter-heads and envelopes.
How to Make Rubber Stamps.
—The Materials Needed.
—To make rubber stamps you will need (1) one or more fonts of type; (2) a composing stick if you intend setting up more than one line; (3) a frame called a chase, 4 × 5 inches on the sides made of a strip of wood 1 inch wide and 1³⁄₁₆ inch high, which is the height of type from its feet to its shoulder; (4) another frame, called the matrix frame, made of a strip of wood 1 inch wide, ³⁄₈ inch thick and 4 × 5 inches on the sides. These two frames are shown at A and B in [Fig. 74]. (5) Two smooth boards 1 inch thick, 6 inches wide and 7 inches long; (6) a tooth-brush; (7) a couple of pounds of dental plaster of Paris, and (8) a ¹⁄₄ pound of pure unvulcanized rubber.
Dental plaster is finer than the ordinary kind and you can buy all you will need from your family dentist for 5 or 10 cents a pound. Unvulcanized rubber for rubber stamps comes in sheets about ³⁄₁₆ inch thick and is sold under the name of signature stamp gum and you can buy it for about $1.00 a pound.[72]
[72] You can buy signature stamp gum of The Goodyear Tire and Rubber Company, 10 Central Park West, New York City. In ordering of this firm ask for No. 4093, ³⁄₁₆ inch thick.
Fig. 74. the matrix frame, chase and boards for making rubber stamps
Unvulcanized rubber is crude india-rubber mixed with sulphur and when this is heated it gets very soft and can be molded by putting it under pressure; when it gets cold it is not only much stronger than before but it is very elastic as well.
Making the Mold.
—Since you know how to make pewter castings and how to set type, making a rubber stamp will be as easy as rolling off a log.
When you have the type set up that you want to make the rubber stamp of, put a lead[73] on each side of it, oil it all over with sweet oil and tie a string around it tight. Lay the thick, shoulder high wood frame over the type matter you have set and see that it is in the middle of it.
[73] See the preceding chapter on [printing].
Next mix up a little more than enough plaster with cold water in a bowl to fill the frame; stir it with a tablespoon and make it about as thick as sorghum molasses. Pour the plaster all around the type in the frame and fill up the space between them as high as the face of the type. Now let the plaster set,[74] that is, get hard, which it will do in a very few minutes. When it is hard enough to hold the type in place and yet before it gets solid take the tooth-brush, dip it in water and brush away the plaster until it is exactly even with the frame, and hence, even with the shoulders of the type as shown in [Fig. 75].
[74] When calcium sulphate is heated it loses its water of crystallization and forms a powder, which we call plaster of Paris; the plaster has the power of taking up water and forming a solid substance, and this process is called setting.
When the plaster has set hard oil the face of the type and the plaster with sweet oil; now lay the thin frame over the thick frame; mix up some more plaster with water and make it thin enough so that it will flow easily into every little space of the type and fill the frame up with it.
Let this frame stay on the lower frame over night so that it will get very hard and you can then lift it off, when a very sharp impression of the type faces will be formed in it shoulder deep, that is as deep in the plaster as the face of the type is high. This frame with its plaster impression is called the matrix.
Fig. 75d. the type in the chase. e. plaster of paris impression in the matrix frame
Vulcanizing the Rubber.
—Cut a piece of the unvulcanized gum rubber ¹⁄₄ inch wider and longer all round than the impression of the type; peel the strip of muslin from the strip of rubber gum and lay it on the matrix. Put one of the boards on top of the rubber and the other on the bottom of the matrix and screw them together tight with the iron clamps as shown in [Fig. 76].
Half fill a kettle with water; lay the mold on top of the kettle—but not in the water—and put both of them in a hot oven for 30 minutes. When the rubber gum gets hot it softens and the pressure of the screws forces it into the letters of the matrix and so makes rubber type of them. The steam from the kettle will keep the wood from charring and the rubber from burning but has no other action on it.
Fig. 76. the matrix with the rubber gum in place ready to vulcanize
The heat vulcanizes[75] the rubber gum and makes it springy and stretchy, but if it gets too hot it will become hard and you will have hard rubber instead. To get just the right degree of heat a vulcanizer,[76] which is simply a little boiler with a thermometer on top, is used by rubber stamp makers.
[75] Vulcanizing is the process of heating raw India rubber with sulphur; the sulphur combines with the rubber to form a new compound. If a large amount of sulphur is used and great heat is used hard rubber, or vulcanite, or ebonite is formed. If a small amount of sulphur and a low heat are used the elastic rubber that is so common is formed.
[76] The S. S. White Dental Mfg. Co., 5 Union Square, New York, sells them, and unvulcanized rubber as well.
Mounting the Rubber.
—All that you need to do now is to trim off the edges of the rubber stamp with a pair of shears and mount it on a smooth block of wood having a handle as shown in [Fig. 77].
Fig. 77. the rubber stamp ready to use
How to Use a Rubber Stamp.
—A special kind of ink is used for rubber stamps, as writing ink is too thin and printing ink spoils the rubber.
To Make an Ink Pad.
—Cut out two blocks of pine wood each of which is ¹⁄₄ inch thick, 2 inches wide and 3 inches long; cut out four strips of woolen cloth 2 × 3 inches, lay two of the strips on each block and then cover the latter by gluing a piece of muslin over it.
Pour a dozen or 15 drops of rubber stamp ink on each pad and rub the surfaces of both of them together to distribute the ink evenly. When not in use keep their inked surfaces together and in a box so that the dust will not get on them.[77]
[77] You can buy a good rubber stamp pad for a quarter. Rubber stamps, pads, and ink can be bought of the Everson and Reed Co., 88 Chambers St., N. Y. C.
To Make Rubber Stamp Inks.
—A Black Ink.
—Mix 3 parts of lampblack with 7 parts of olive oil.
A Red Ink.
—Mix 2 parts of vermilion with 3 parts of olive oil.
A Blue Ink.
—Mix 3 parts of aniline blue and 6 parts of oleic acid with 94 parts of castor oil.
A Green Ink.
—Mix 25 parts of aniline blue, 15 parts aniline lemon yellow, 50 parts oleic acid and castor oil 950 parts.
How to Make a Copygraph Pad.
—A copygraph pad, or hectograph, as it is often called—from the Greek hekaton which means 100, and graph to write, hence to write a hundred—is a gelatine pad for duplicating a letter or a drawing.
To use a copygraph pad you must write your original letter with an aniline ink; then you lay it on the pad and rub it down with your fingers. When you remove the sheet an impression will be left on the face of the pad and if now you lay a sheet of clean paper on the pad, rub it and pull it off you will have a copy almost as bright and clear as the original. In this way as many as 50 or 100 copies of the original letter can be made.
To make a copygraph pad put 1 ounce of the best gelatine in enough water to cover it and let it stand for 24 hours. Put a tablespoonful of table salt into a cup of water, pour it into the outside can of a water jacketed pot. Put 6 ounces of glycerine in the inside pot, set the pot on the stove and heat it good and hot, or to be exact, to about 200 degrees Fahrenheit.
Drain off all the water from the gelatine and put the latter in the glycerine while it is yet on the fire; stir the mixture slowly every once in a while in order to prevent bubbles from forming, and skim off the froth that forms on top of it. When you have a nice smooth mixture stir in a teaspoonful of oil of cloves to keep it sweet.
Next make a pan of sheet zinc a little larger than the letter you want to copy and ¹⁄₂ an inch high, or you can use a tin pie pan if you merely want to try it out. Set the pan on a level table, fill it with the hot mixture, let it stand over night and it is ready to use.
How to Copy a Letter.
—You must write your letter with a special aniline ink, called hectograph ink, and use a new steel pen to do it with.
While the writing is getting dry take a small clean sponge, wet it with cold water, squeeze it as dry as you can, wash the face of the gelatine with it before you try to make an impression or else you will spoil the pad.
This done, lay the sheet of paper with the written side down on the pad and gently rub your fingers over every part of it. Let the paper stay on the pad for a couple of minutes, then grip a corner of it and pull it slowly and evenly from the pad as shown in [Fig. 78]. Now you are ready to make your copies.
To do this lay a clean sheet of paper on the pad, rub it as you did the original, let it remain for a minute and pull it off. Keep on making copies until you have as many as you want or the impression gets too faint.
Fig. 78. pulling an impression from the copygraph
When you get through pulling copies wash the face of the pad with a moist sponge and let it dry thoroughly before you make a new copy.
How to Make Hectograph Inks.
—Black Ink.
—Mix 10 parts of methyl violet; 20 parts of nigrosene; 30 parts of glycerine; 5 parts of gum arabic and 60 parts of alcohol. Heat it until the anilines are dissolved and stir until all are thoroughly mixed.
Red Ink.
—Mix 10 parts of fuchsin, 10 parts of alcohol; 10 parts of glycerine and 50 parts of water. Heat and stir as before.