The fact that risography is not necessarily compatible with every print job is certainly due to the fact that the print results are often too inconsistent to reliably overcome all errors in the process. While the best results are achieved if the projects are prepared with the risograph in mind instead of as an afterthought, in some projects this is more noticeable than in others.
When prints are stacked together after being ejected from the machine, colour can be transferred from the sheets on the bottom to the ones above them. Even when cutting the sheets or further printing on the sheets, pressure is exerted that can rub off the colour. One way to avoid this is to place sheets between prints that are removed before printing, leaving the back of the sheets dry. The same applies to sheets that have a high ink coverage—these are sure to have traces of excessive ink coverage. The best results are achieved with prints with up to two colours on heavier paper.
A plastic needle inside the risograph helps detach the papers from the drum and transport them further along to the paper ejection. Heavy ink coverage causes the needle to scratch over the freshly printed sheet, needlessly spreading the ink and smearing the print. Depending on what the subject looks like, this may lead to visible traces.
For double-sided printing or printing on ready-printed sheets, the rubber wheel of the paper feed is a particular problem. This is described in detail in sub-chapter M.
Because the colours are applied to the paper as layers one after the other, the register of the sheets can never be one hundred percent accurate. If high registration accuracy is desired in the print image, then adjoining contours of the subject should be overfilled in advance.
For many reasons printing with a specific colour drum can lead to a skewed print image. While recalibrating a drum is very hard to achieve and won’t always lead to promising results, a possible solution can be to print a new master, but skewed as well—on purpose. By measuring the amount of skew (in degrees; for example with a triangle ruler) and skewing the separation in the opposite direction before creating a new PDF it might help to produce an evenly placed print image. It can definitely help to either print a smaller image or to use a bigger colour drum or, if possible, not print all until the edges of a master foil. The smaller the image (and the more centered on a master sheet), the less noticable the skew will be. For example: It might help to print an A4-sized multi-coloured image with a colour drum in the size of A3 instead of A4.