Polymetaal

The Papers used in Printing.

Generally speaking one can make a distinction between paper that will allow, when printed, for a relief, due to the plate used in printing ( intaglio plates) and the paper that is used for printing planographic work. The former is "tallle-douce" paper. This paper will bear the "plate mark" and will be pressed into the intaglio lines of the plate. In fact, all of the papers which are used for embossing or goffering belong to this category. T aille-douce paper must be used when damp and must bear up under the dampening and soaking procedures. The second type of paper, which is used in planographic work, serves the purposes of lithography, serigraphy, offset and, to a certain extent, woodcut.
These two categories of paper must also be analysed in terms of their receptiveness to printing and, finally, in function of their quality since very often prints require paper that will enrich their appearance.

1. PAPER FOR ENGRAVINGS:. The paper used for printing engravings must always have specific characteristics, above all, because it is compressed by the press and will only print correctly if the paper penetrates the lines of the plate. This paper must therefore be very elastic. It must take well to being compressed and have an homogenousness and a fairly strong body ( i. e .a fairly low density in comparison to its mass) .The paper surface must be soft to the touch but it must not be finished nor, above all, must it be coated. In selecting a paper to print on, the printer must choose in function of the relief he will need as determined by the plate to be used. Quite obviously finely etched plates will not require the same kind of paper as a deeply cut engraving. Fine etching requires soft, silky, and light paper whereas engraving calls for a heavier, more resistant, and elastic sheet of paper. Furthermore, one must bear in mind the thickness of the plate itself since a one millimeter thick plate ( 0.039 in ) can easily be absorbed by light laid paper, but if the plate is thicker one must have recourse to a thicker and more resistant sheet of paper. The smoothness of the paper to be used must be chosen in function of the type of lines to be printed. Very fine lines must be printed on a very soft and homogenous surface such as a satin finish laid paper. Thicker lines can be printed on slightly grained paper.
Wide lines that are not very deeply cut require supple paper since a stiff paper will not pick up all of the ink out of the lines of the plate. Suppleness, elasticity, compressability, and satiny finish are all characteristics of rag paper (called laid paper) weighing from 100 to 300g/m2. If very deep goffering or stamping needs to be done only a heavy, strong paper can, be used such as thick rag paper or corrugated paper weighing up to 600g/m2 (such as the "esportazione" paper of Fabriano or the "extrarugueux" of Arches) . One may also, however, use extremely malleable papers treated with "Pulpex" which resist all kinds of manipulations and take particularly well to hot stamping.

Paper used for printing engravings must be very absorbant, permeable, only slightly sized and never coated. This is because engraving paper must often be dampened in the printing process. Their wettability must be such that they will resist traction and compression when damp, and that they will go back, to their former state after drying. It is not absolutely necessary that the paper be very thick but the pulp used must be well mixed. Pure rag paper is the paper that will take best to dampening. It might be mentioned that rice paper, Japan paper and some Dutch papers ( in particular the Van Gelder (koperdruk) vellum paper for intaglio printing) are extremely absorbant and therefore should be dampened with a sponge. The new types of paper containing pulpex can, on the other hand, be used for intaglio printing without being dampened even though they take well to dampening .

Since the paper used for printing engravings must show up colours without artefice or brutality it is best that it be of a natural white colour not unlike the creamy white of linen or cotton. The different whites obtainable in rag paper are subtly varied and thus the printer will have to choose the tonality best suited for the engraving to be printed.
Paper used to print intaglio plates must not be subject to alterations or degradation. Because of this it must be made from a rich pulp containing a high percentage of rags. In fact the rag content guarantees resistance to the adverse effects of light, humidity, and dryness. Since this type of paper is usually used when printing with traditional inks containing linseed oil it is necessary that the paper be absorbant without, however, letting the ink show through. Mat finish, satiny, and slightly grained papers must remain permeable.
Moreover, it must be pointed out that the paper used for printing intaglio work should be "beautiful paper" because a print is not just a reproduction but rather an original creation. A nacre finish Japan paper, a satin finish laid paper with a deckle edge, or a creamy vellum paper add much to an engraving's beauty. In fact, it is hardly exaggerated when a specialist admires beautiful margins or a water mark that takes up the entire sheet of paper.

2. PAPERS USED IN PLANOGRAPHIC PRINTING. Although this paper does not have the same characteristics as the papers used in printing intaglio plates it must still be chosen in function of certain criteria.
First of all planographic prints always turn out best when printed on high quality paper. This is due to the durability of such paper, as we have already seen. It is also a good idea to use a rag base paper or then at least some type of paper which contains a high proportion of rags.
These papers can be classified in two broad categories: deckle edge papers that are either hand made or then unsquared if machine made and, on the other hand, squared paper. Only squared paper can be used on mechanical presses especially when several colours are printed and registering becomes necessary. In fact, dekle edge paper cannot be properly registered on an automatic press. Nevertheless, deckle edge paper can be used perfectly well for printing woodcuts, lithographies, pochoirs, and monotypes if the printing is done manually, either by rubbing or with a traditional lever press. In serigraphy one can use deckle edge paper if no registering is required. If colour impressions are to be made the sheets of paper will have to be squared in order to superimpose the colours precisely. For offset work, lithographic work on mechanical presses, typography, automatic serigraphy, etc. the sheets of paper must be squared. At times it seems a real shame to cut the deckle edge of a beautifully made sheet of paper but it is important that the paper catch well when it is printed on.

The paper used in lithography must be absorbant in order that it take on both the oily inks and the water. Usually such a paper has a mat finish which is not at all fluffy. It should also have a very even satin finish since a grain that is too pronounced will refuse solid colour applications and may damage the half tone areas. In the past litho paper was laminated after being dampened so as to polish the surface. This kind of work was done sheet by sheet between two polished zinc plates. After this calendering the sheets of paper were pressed in packets of 25. In chromolithography the sheets were calendered in order to give the greatest possible precision in registering. Coated and sized papers were much used in commercial lithography as well as simili Japan paper, which is smoother and more rigid than real Japan paper (the latter being preferred for quality work). For map printing a special type of paper was used which was insensitive to humidity.

In offset printing the paper used must be both well squared ( in the direction of the machine) and very flat. Furthermore, such paper must have an average humidity when used and, although it must be absorbant, it must not be porous. Actually the more absorbant varieties of paper are not the ones that are more permeable on the surface. The "chromecoat", for example, is extremely smooth and yet very absorbant while blotting papers are less so. This is due to the fact that the capillary action of well laid paper is finer but greater and thus it takes an ink more readily than other papers. Offset paper must not be magnetized nor must it be very acid.

In serigraphy the levelness of a sheet of paper is a fundamental requirement. An irregular surface or a surface that is too grainy will cause problems in printing. The paper is chosen in function of the type of ink to be used ( a great variety of them are used in serigraphy! ) .Water base inks require a thick paper, very slightly sized if not at ail, which must in no way be coated. The paper must be capable of good absorption but must also dry without being deformed. The papers used for oil base inks should be chosen in function of the effect to be obtained: absorbant mat finish paper will give a mat finish whereas heavily sized smooth paper which is also coated will result in a shiny finish. Shiny inks must be printed on shiny papers.
Very heavy, thick paper or cardboard must be extremely level and smooth if they are to be used in anyone of the above printing techniques nor must they be excessively sized .