Posted: 17 Oct 2014 14:10 by paperpusherLast edit: 17 Dec 2014 20:02 by issuepress
To understand the role that paper plays in Risograph printing begins with a brief knowledge of ink behaviour. Soy-Based Risograph Ink dries through a combination process of absorption and evaporation, so it is ideal to find paper stocks with qualities that suit this process. Much like soy-based newspaper printing ink, Riso Inks may smudge after the prints have dried (technically, the ink never really sets). This may be of concern for some projects, especially those with heavy ink coverage, or intended for handling. For example, when printing a publication cover, no paper will ever bring about fully satisfactory results if printed with heavy coverage. Covers are best suited to lower percentages of ink usage, fine-line, or ultimately a lamination/varnish process.
While standard bond paper will accept ink, its smooth surface does not allow for full absorption, and so its potential for smudging is much greater. The key terms one should look for when considering paper types for Risograph printing are: Vellum, Offset, and Hi-Bulk. Newsprints, kraft, and construction papers, of course work quite well as they are very absorbent stocks.
While the Riso can accept a range of paper sizes, from 3.5x5.5" to 11x17", it can be difficult to find suitable stocks with the above mentioned qualities in cut-sheet sizes. Thus, it is ideal to make custom purchase orders of press sheets which can be custom cut to size. The paper supplier should be able to cut to size for a small fee. Oftentimes there are offcuts leftover when larger sheets are cut down. One should always ask the supplier to include these offcuts in the delivery as they prove useful for smaller projects (one might even be able to produce an entire book using offcuts alone).
Note: Paper grain should be taken into consideration when considering how many cut sheets you will get out of a larger press sheet. Grain direction should always run parallel to the spine of book, especially when perfect bound, and this requires that you plan the imposition accordingly. It may help to create an illustrator file that accounts for all the sizes that you are playing with: Press Sheet, Cut Sheet, Final Dimension of Print