A perfect dry mat must have the following properties or characteristics:
(1) It must always be of the same thickness. This means that not only must all the mats in any given lot be uniform in thickness but that from lot to lot, the mats must be the same. And it is particularly essential that each mat be of uniform thickness throughout, in other words when measured with a micrometer at the corners or in the center or along the edges, the thickness must be the same.
(2) It must always be a completely finished mat, which means that it must be coated before leaving the factory, thereby eliminating all necessity of applying coatings, oils, fats, gasoline, etc., in the newspaper foundry.
(3) It must have a smooth glass-like surface without any trace of fiber or web marks. This smoothness of surface must not be accomplished through calendering to such an extent as to make the mats too hard. The harder the mat, the more pressure needed in molding it and more danger of breaking the type. The mistake is often made of calendering the mat until it is hard as iron in order to give it a smooth face and to be able to claim that it can be used with less backing. While less backing means somewhat less work, this slight saving of labor in the stereotype department is more than offset by the loss incurred by ruining expensive case type, and is entirely out-weighed when poor printing results through missing letters that have been forced down under molding pressure is considered. In the perfect mat, smoothness of face is achieved in a natural way in the machine during the process of manufacture. In any case, calendering is deleterious; glazing the mat should be all that is necessary.
In the matter of “stay back”, manufacturers in all countries where dry mats have been and are being made have tried to make dry mats that would require little or no backing. To date none of these experiments have been successful and manufacturers are back to where they started. Experience has shown that any slight advantage through saving of labor obtained with a mat that requires less backing is out-weighed by the disadvantage of ruining type, extra fuss in the handling, and above all, in poor printing plates produced.
(4) The fibers of the dry mat must be lightly felted and interwoven on the machine, thereby giving flexibility, elasticity, and tensile strength; they must not be compressed.
(5) Perfect mats must be loft dried, a very expensive method but the only one to get the best to the user.
(6) A dry mat must be the product of meticulous care in the process of manufacturing, of absolute cleanliness in the factory, as the smallest particle of grit will spoil the finished mat.
In summing up, the perfect dry mat must have all the advantages of its mother, the wet mat, excel her if possible in any particulars, and inherit none of her drawbacks.