Vulcanizing Flask Clamp.
A large sized gas heated press, such as made for the purpose of manufacturing rubber stamps, is shown in the next cut, [p. 53]. Its construction is obvious. It is termed by the trade a vulcanizer. Its manipulation will be given further on.
Type are generally the object to be copied. These are best set up with high quads and spaces. Naturally rather a large type is chosen, with extra wide spaces between the letters. Some advise rubbing the type faces full of hard soap, afterwards brushing off the face, leaving the hollows filled. Sometimes wax is recommended for the same purpose. This prevents the plaster of the matrix entering so deeply into the cavities of the letters.
Gas-heated Stamp Vulcanizer.
The type forming the model to be reproduced, is locked in a frame. Two pieces of printers’ furniture or other wooden strips screwed together by wood screws at their ends will answer for a locking frame for small inscriptions.
The model to be copied need not be type, but any desired relief may be used, such as an electrotype, a stereotype, an engraving or another rubber stamp. In any case it is to be placed upon a flat surface, best an “imposing stone” or piece of marble, with the inscription upwards. On each side of it distance pieces reaching about one-eighth inch above its upper surface are to be placed.
The next shaping appliance is the matrix or mould, or reverse of the model which is to be copied. This in the case of rubber stamps is properly called the matrix. Those who have witnessed the stereotyping of a large daily newspaper have seen the matrices of the type made of paper and paste, the whole mixture being termed “flong.” Such a matrix is required for rubber type, but paper is rather too susceptible to heat although good work can be done with it. It also does not enter as deeply into the cavities of the type as is desirable. As a rule a fine quality of plaster of paris is to be recommended. What is sold as dental plaster is the best, but common plaster can be used. It is mixed with water or with a solution of gum arabic or dextrine in water. For the latter enough gum should be added to make the mixing solution as thick as thin syrup.
A piece of iron, perfectly flat and true, is now to be taken, large enough to more than cover the inscription to be copied. Upon its surface a putty made of the plaster and the liquid used in mixing is to be spread. This should be rather stiff. The surface of the iron should not be too smooth as it is desirable that the plaster should adhere well on setting. The plaster should be smoothly spread to a depth of three-sixteenths or a quarter of an inch. It is best applied with a palette knife or trowel, although a table knife will answer perfectly. If its surface does not become smooth it can be made so by applying a little of the solution with the knife or trowel.
Before this has been done the model must be oiled. Olive oil or other clear oil is applied to all parts of the type faces, and the excess is then wiped off and cleared out of the interstices with a piece of blotting paper.