PAPIER MACHÉ MATRICES.
The stereotyper for daily newspaper work uses very generally the papier maché or “flong” process of reproducing the page. This is also available for rubber stamp making.
The first requirement is paste. This is made by softening twelve parts of whiting in forty parts of water, letting it soak for an hour or more. Nine parts of wheat flour are added. This is best mixed with a little water before adding to the main mixture. It is then brought to the boil and seven parts of glue softened by soaking in twenty-one parts of water, are added. For each gallon of such mixture, one ounce of white crystallized carbolic acid is added if it is to be kept for a long time.
The “flong” is made by pasting together, one on top of the other, a sheet of fine hard tissue paper, three sheets of blotting paper (about 23 pounds to the ream), and a heavy sheet of manilla paper. The pasting must be smooth and each layer must be pressed and rubbed down, but not too hard. It is very important to secure perfect smoothness and regularity, and entire absence of air bubbles.
Every printing office where the process is used has its own traditions as to the preparation of flong. As a great deal depends on manipulation, it would be well to endeavor to inspect its practical use in a newspaper printing office before making it. Ready prepared flong can also be procured.
The form of type must be very clean and there must be no paste on the tissue paper face of the flong. The type are lightly oiled, some powdered talc is dusted over the damp tissue paper face of the flong, and the mass is laid face downward on the type. With a stiff haired brush the paper is now beaten down against the type. Great care must be taken to beat vertically; a slight side action will ruin the resulting matrix. If the brown paper will not stand the beating, a cloth may be spread over it.
The progress of the work can be watched by raising up a corner from time to time. When sufficiently deep the last touch is given by the printer’s planer. This is a block of hard wood. It is placed upon the back of the flong and is hammered down. The operation is repeated until the entire area has been treated. For much rubber stamp work the area would be so restricted that shifting would be unnecessary.
The work is then put into a heated screw press, such as the vulcanizing and matrix press, and is dried for a period varying from some minutes up to half an hour. Some blotting paper is advantageously pressed on top of the whole in the press while drying. The press is opened, the flong removed, and dried in an oven. It is kept under a piece of wire net while drying to keep it flat. The net may be of wire, .064 inch thick, with six meshes to the inch. This baking is not strictly necessary for rubber stamp work.
This gives a matrix which may be used as rubber stamp moulds. In use it is recommended to place a piece of smooth tin foil over it. This tends to give a smoother surface to the rubber.