When selecting the right paper for reproducing prints on the risograph, the surface finish is particularly important. Papers from both categories, wood-containing and wood-free, are refined after production using various techniques to change the surface properties of the paper. A distinction is made between machine finished papers (papers left untreated after they come out of the machine, rather rough and the top and bottom (ie felt and screen side) is easily recognisable in most cases), satin papers (papers with closed, glossy and smooth surface), coated papers (papers with a pigmented coating layer, either glossy or matte), embossed papers (papers that obtained their ribbed, grained or hammered structure with the help of embossing calendars) and coated papers (papers with plastic- or varnish-coated surfaces, which may even be smudge- and waterproof). Since the toner used in digital printing stays equally well on coated and uncoated paper, surface quality is less of an issue in digital printing. However, it is crucial when using a risograph. In digital printing, the toner is fixed in the last step of the print process with the paper passing through a fixing unit (two rollers, one for heating, one for pressure). 1
Up to 200 °C heat and the pressure effect ensure that the toner powder bonds with the paper before the heated prints come out of the digital printer. Since the risograph uses ink, not toner, this ink cannot be fixed in a process like that, so the structure of the paper is solely responsible for the ink sinking into the paper. Coated papers are therefore out of the question. The rule of thumb is: “the more absorbent, the better,” especially for subjects with high ink coverage.
Jackson Lam, founder of Hato Press, a renowed riso printing and workshop studio in London, comments: “It forces the artist or designer
to really delve into uncoated paper stocks, for which there are hundreds, and find papers that introduce added context to the project.” 2
Standard laser paper will work with the risographic ink, but the surface will not be able to absorb it completely, so the ink remains slightly moist and might come off. As a result, drying and finishing times are extended and depending on the ink coverage, it has to be assumed that the ink may not even dry and come off when coming into contact with skin or when sheets are stacked. If a coated paper were to be used in a risograph, the ink obviously would not be able to penetrate the paper structure because the coating layer of the coated papers prevents or at least impedes it. It is very likely that the ink will smear, either during the printing process within the machine or afterwards when touching a sheet.