A technical dictionary of printmaking, André Béguin.
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Blanket
[1] In connection with the intaglio press one uses blankets, or felts (usually plural as several of them are needed), which are made of a high grade wool cloth which is "white and lacking a hem, list, or selvage" (A.Bosse). These blankets are used when printing and are placed between the two rollers and on top of the paper to be impressed. Bosse mentioned the fact that "some curious printers also use a few blankets of double-faced thin serge which are placed on the plate" so as to further reduce the pressure. The role of the blankets is to soften the strong pressure of the rollers as well as to distribute the pressure evenly all over the plate. Usually three or four blankets are used. In order to do the job properly they must first be passed through a press a great number of times. It is only after such use that they become compressed and homogenous and take on a texture not unlike felt. In fact the process is also called felting. The least used blanket should always be placed at the bottom of the pile, which means that it will be in direct contact with the paper. The most used blanket should be on the top of the pile and therefore in direct contact with the roller of the press. When the blankets are piled up arange them so that the second one will hang over the first one (on the roller side), the third one hanging over the second, etc. so that the roller will "catch" more easily when printing begins. In his treatise on photogravure Martelle-Thièle recommends having new blankets fulled by professional printers and even suggests exchanging a new blanket for an old one, which will make both parties happy. It is quite true that new blankets do not give a good result especially insofar as concerns large prints, thin lines, dotted work (as for example aquatint ), or also when the lines are deep ones with slopes that are more or less vertical. In fact, new blankets are still too soft and thus do not follow the dips and hollows of the lines cut in the plate. It can happen that when new blankets are used parts of a line will not be printed, thus giving rise to blind printings. At times it is possible to get blankets which look like felt and are thicker than usual, in which case only one or two layers are needed. Although they are better suited to receiving pressure these blankets also present some drawbacks. In fact, if they are not kept up perfectly they become stiff, take on plate marks and then leave marks on the impressions as well as distributing the pressure irregularly.
Personally, I have used blankets made of oilcloth for years (the type that can be found in any large department store). Oilcloth can be bought in rolls or by the meter. The advantage of using oilcloth is that this material needs no tricky upkeep and above all no fulling (felting). Furthermore, such blankets can be washed whenever spotted (with gazoline on the plastified side) and, above all, they are very elastic since they can he pressed in every which way and with any pressure and still return to their original shape. The best oilcloth for printing is the thickest one which imitates leather but does not have the wrinkles imitating leather. Three layers are needed for printing but in the case of aquatint this may be increased to four. The top and bottom layers should show their plastic sides, in other words the bottom one should have its plastic side against the paper to be printed while the top one should have its plastic side in contact with the press roller. The cloth side should not be visible. In this way you will always have clean blankets which can be used for a long time. The cloth side (non plastified side) may also be layed onto the paper so as to increase its suppleness but in such a case add a sheet of paper so as not to get cloth marks on the print. The suppleness of these blankets is such that they facilitate the penetration of the paper into all of the lines made in the plate. Rubber blankets are also used and even blankets made of nylon.
Cloth blankets soak up the humidity of the paper and, in the long run, become stiff due to the sizing that is transferred from the paper to the water. To wash the blankets soak them in lukewarm water (some people recommend cold water) without any soap or detergents in it. When they are removed they should be squeezed by hand but not wrung and then rinsed several times. Then hang them up and let them dry several days. Before using them make sure to "twist and rub them so as to rumple them and make them soft" (A.Bosse). When the work with them is over (printing) spread them out and let them dry.
[2) When used in offset presses the blanket is a cylinder, covered with rubber, which acts as an intermediary between the plate and the paper being printed. [* printing techniques , offset].
[3] When paper is made by hand the blanket is a white felt which receives the paper pulp as it comes out of the form where it is shaped. The blanket is used to distribute the pressure on the paper and to rid of excess water. [paper].
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