Dry Pulp For Mats
( Originally Published 1927 )
In 1863 the idea of using dry pulp appeared for the first time. This method of manufacture was not practicable, too difficult and these mats could not be made on a commercial scale.
The first attempt to use a dry cold process and to mold by rolling a mat only once was made by GEORGE EASTWOOD, of Kingston-upon-Hull, County of York, England, in 1887. It retained certain features of the wet mat but introduced the idea of a dry mat process, and should be designated as a semi-dry mat.
The text of the specification of the patent granted to East-wood explains his process in the following manner:
"According to my invention I follow what is practically a dry process in the manufacture of the matrices, so that the heating of the type can be dispensed with, and I back up the blanks with sand during the ordinary process of warming and drying the matrices, and I thereby obviate the liability of the blanks to become flattened by the pressure of the molten metal used in taking the castings.
"For the purpose of my invention I make a mold of two parts—namely, a facing and a backing. The facing is composed of two or more sheets of tissue-paper or other like material pasted together with a composition containing glycerine and a suitable starchy material, which composition keeps them in a flexible and elastic state, prevents the paper from becoming too hard before use, renders it sensitive to moisture, greatly reduces the contraction on application of heat and hardens the matrix or mold when heated. The backing consists of a dry thick sheet of soft paper, blotting paper, felt, or other like suitable substance capable of receiving and retaining an impression, and one side of which when used, is covered with a thin sheet of soft paper which is thinly coated on both sides with an adhesive material.
"In taking the matrix the facing is placed upon the type and the back of the facing is then covered first with a piece of muslin or other suitable thin textile material and next with a woolen or india-rubber blanketing, which (except when of India rubber) is preferably used warm. The whole is then rolled or pressed. This having been done, the blanketing and the muslin are removed and then the backing is placed upon the back of the tissue-paper that forms the facing. That face of the backing which bears the composition being put in con-tact with the tissue-paper, the composition on the backing should be nearly dry. The blanketing is placed upon the backing and the whole is again rolled or pressed. The matrix is at once formed and when removed from the type has simply to be warmed through to harden the composition."
"Instead of the two rollings or pressings above described one rolling or pressing will suffice if the backing be placed upon the facing, in the first instance, with the blanketing over them, the use of the muslin in this case being dispensed with; but a good result is not so certain."
This was the basic idea of a dry mat. It was not until after six further years of experimenting that Eastwood invented a dry mat which was the first dry mat in the present day definition.
Shortly after Eastwood had made his first invention, DIEDRICH SCHNEIDER and ARNOLD SCHOTT, of Philadelphia, in 1888 invented certain new and useful improvements in stereotype matrices. The invention was made to provide a mat from which an impression can be made at any time in a dry state, no drying or hardening being required, that would be so durable and strong as to resist the pressure of the quantity of metal on the blank spaces. To attain their purpose the inventors made a semi-dry mat. The invention consisted in a matrix composed of a sheet of fabric (cotton-batting, flannel, lint) coated and partly impregnated with a semi-dry plastic mass and provided with a backing of pulp. This plastic mass was made of glue, syrup, glycerine and a powder (alum, flour, chalk, asbestos-powder). This plastic was coated on a sheet of fabric and on this sheet another of very thin fibrous paper, for example Japanese vegetable-fibre paper, was placed. This mat is pressed upon the matter to be stereotyped and a sharp, clear impression of the type in the fibre paper and plastic is produced.
The matrix remains on the type and a sheet of wood pulp or any other pulp is placed upon the matrix, which sheet has been impregnated or saturated before being applied with a mixture of two parts of powdered dextrine, one part of starch, and one part of asbestos powder mixed with cold water and boiled and stirred until it has the consistency of cream. By re-applying the pressure the pulp is caused to adhere firmly to the matrix and to stiffen the same, so that when the hot stereotyping metal is applied it does not press down the matrix at the blank spaces. The matrix is removed and subjected for a few moments to a current of hot air for the purpose of hardening it. The improved matrix does not warp or shrink, and the impressions are not injured or marred by hardening the matrix. The inventors claimed that "by means of our improved matrix, stereotypes can be made very rapidly, as the matrix need not to be dried on the type and the type and matrix need not to be heated, as has been necessary heretofore, while using composition or wet paper for stereotyping. There is not need of separately backing the spaces with plaster of Paris or compositions or cutting them out, as has been necessary heretofore."
"By using our improved matrix the type is not injured by heat as it is by the old method of stereotyping. As we do not heat the type no time is lost by waiting for the cooling of the type in order to procure a second or more moldings. A saving in time is effected, from 6-10 minutes."