Present day dry mats are integral homogeneous units, delivered in sheet form of one standardized size, twenty by twenty-four inches. They are made in any thickness between the limits of twenty-four thousandths and forty thousandths of an inch to meet the preferences and needs of stereotypers under varying conditions, and for use in all kinds of equipment. They are not laminated or pasted together and hence cannot blister or blow up; neither do they deteriorate either before or after molding.
By their very nature dry mats at once eliminate one phase of drudgery in the foundrythat of paste mixing and pasting wet mats. Dry mats are delivered in standard cases containing five hundred mats, wrapped in waterproof paper. In extreme emergencies the mats may be used just as receivedright out of the cases, but in every day practice and for uniformly good results they require a simple process of conditioning.
To properly condition dry mats, they should be placed, preferably in a heatless humidor for from twenty-four to forty-eight hours, depending upon conditions prevailing in each plant. It will require a little experimenting on the part of the stereotyper to determine just how long to keep the mats in the humidor so as to get the desired results as to shrinkage as well as the proper depth in molding.
Those who prefer to steam their mats in humidors may do so without any harm to the mats or to results. However, with a perfect dry mat all heat should be turned off. Good dry mats absorb all the moisture they need from the humid air caused by the evaporation of the water in the pan at the bottom of the humidor. Whether dry mats are steamed or not, from the humidor they should be seasoned in storage boxes for from at least five to ten days. Consistently conditioning and seasoning dry mats insures even distribution of the moisture put into the mats, means even depth in molding, and consequently good printing plates. Experience in many hundred newspaper plants have conclusively shown that those who condition their mats consistently are the ones who get uniformly good printing results.
Halftones should be underlaid with one layer of newsprint paper so that they are four-thousandths of an inch more than type high. For taking the impression, the conditioned mats are imposed on the forms face down, and a molding blanket (either cork or felt: some stereotypers prefer two blankets, both cork or one cork and one felt) placed on top. The mats on the form are rolled one way (but once), the stroke of the roller bed being from twenty to thirty seconds; the slower the better. The mats are’ then removed from the forms, and the forms do not enter into the process any further.
The molded mats are now “backed up” with felt packing in the particularly open spaces, and in the same way as the old wet mats. This is done so that the mats can withstand the force and weight of the metal in casting the plates, as otherwise the mats would give way in these open spaces and cause smudges in the printed pages. After they are “backed up”, the mats are thoroughly dried in the roaster or scorcher from one-half to one minute. A thorough drying is essential and prevents many of the troubles which stereotypers other-wise encounter in their work. Once the dry mat has been impressed, the form no longer enters into the process. The forms have not been heated in any way, nor have they been subjected to any pressure other than that of the mat roller in molding, and are therefore immediately available for re-make or other disposition. Since the molded mats are still moist, they must be thoroughly dried preparatory to casting, as otherwise the heat of the metal in casting the plates (generally from 600° to 650° F.) would create steam which would repel the metal from the mats and cause imperfect printing plates. This drying of the mats is done in the roaster or scorcher, which at the same time helps shape the mats to conform to the curvature of the cylinders of the printing presses.
During this drying period the dry mats shrink so that without altering present make-up in any way it is possible to print on narrower paper. With dry mats manufactured in the right way this margin of shrinkage is constant and uniform, and is always under the control of the stereotyper. The normal shrinkage of dry mats should be one-quarter of an inch in width of an eight-column twelve and one-half em page, such shrinkage being usually obtained by twenty-four hours of humidoring. In length of column the shrinkage is usually one agate line but never over two agate lines. When the stereotyper works out these details, such as length of time in the humidor and storage box, and follows them consistently, the shrinkage is always under his control and is constant and uniform.
The shrinkage in width of page is utilized by publishers to save worthwhile sums on their bills for newsprint, without altering present makeup or changing present margins. For example, a paper of eight columns twelve and one-half ems, instead of printing on seventy-two inch rolls, as with wet mat stereotypes, can be printed on seventy-one inch rolls with dry mat cold process stereotypes. This saving of approximately one and one-half percent of newsprint applies to all roll widths, and to all standard size newspapers.
Where shrinkage in length of column is objectionable because of advertisers’ complaints, it is a simple matter to allow for it in the composing room by setting up two additional lines; that is, by making the composition “strong” to the required extent. Since many large dailies now have to make their advertisements “strong” even with wet mats to allow for the shrinkage in the wet mats as well as in the plates themselves, it is no problem whatsoever to allow for the additional shrinkage with dry mats. If a dry mat is properly made, the shrinkage is uniform and it is a simple matter to allow for it.
One of the factors which has mitigated against the more extensive use of dry mats in the past, has been the fact that this shrinkage in width as well as in length of column, was not uniform, and therefore has been the cause of a lot of trouble in the mechanical departments, as well as with advertisers. With good dry mats the cold process of stereotyping has been rid of this bugaboo, and publishers no longer have any troubles on that score.
Then again, shrinkage in length of column is not altogether a disadvantage. In fact it may be taken advantage of and prove a blessing in disguise. It permits of printing two extra lines on the editorial and magazine pages, and particularly on the classified pages, where the rate is generally so much per line, without increasing the actual size of the pages.
The economy as well as the facility of cold stereotyping is not attained at the sacrifice of good printing. This is borne out by the experience of many hundred newspapers through-out the world.
However, facility is not the only virtue of cold stereotyping; together with facility and simplicity there is genuine economy of time and money.