Riso Kagaku Corporation is a Japanese company which is the inventor and distributor of Riso print equipment, specifically the Risograph machines that we print with.
Though it looks on the outside like a copy machine, the Risograph is NOT a copier. It is a duplicator (think mimeograph) with a process like silk screening.
The Riso was marketed for high volume and inexpensive duplicating. And to this day, it is mainly used by businesses, schools and churches who need production runs of 50 to 10,000 prints of the same thing.
Because of Riso’s similarities to screen printing and the availability of 21 standard colors along with 50 custom colors, designers and artists have begun adapting these machines to produce beautiful and unique works.
Riso combines the best of digital and traditional print: a hand-made look and feel with the speed, low-cost and efficiency of a modern printer.
The Riso duplicator internally creates a stencil that is laid onto a drum filled with ink. The drum then spins at high speed, forcing the ink through the stencil onto the paper, where it is absorbed creating a unique look and texture.
Riso printer, Risograph, RISO Printer-Duplicator or also called simply only Riso is a stencil printer designed mainly for high-volume photocopying, duplicating and printing. It sits in the realm somewhere between screen print and offset lithography but with a unique aesthetic. Traditionally, risographs have been used for high volume photocopying in schools, churches and small political parties. It uses soy based inks to produce unique quality outcomes, each screen is made from banana paper and unlike litho printing only takes a single print for the screen to be fully inked and ready for printing. These days we can see the rise of a risograph printers for its vibrant, environmentally friendly and cost effective nature, especially on medium to large runs. It can produce anything from books to artist prints with tactile finish very similar to that of screen and litho printing, but for a fraction of the cost.
The Risograph is NOT a high quality print process- it's a cheap, quick and funky alternative to screenprinting that has inherit limitations to output quality. If consideration is taken on the design side (trapping, overprinting, minimizing ink laydown, etc.) many issues will be calmed.
The underlying technology of a risograph is very similar to screen printing or a mimeograph. It works by creating a thermographic master screen for each color of your artwork. This is then wrapped round a rotating drum. Ink is pushed through tiny holes in the screen and onto the paper, which is fed flat through the machine while the drum rotates at high speed to print each image on the paper.
The process works by printing one color at a time. Multicolor images are created by switching the drum color and running the paper through the machine again creating layers in a process similar to screen printing.