Overprinting is a printing technique where you print multiple colors over each other to achieve a more dynamic image, with a wider range of color.
Here is an example:
from Color by Overprinting, 1955 by Donald E. Cooke
There are several ways to create multiple color “plates”:
- use the “layers” feature in Adobe Photoshop/Illustrator/InDesign, then export a separate PDF for each
- when doing artwork by hand, use a light table to create multiple originals (one for each color)
- For advanced print designers, you can try setting up Riso ink colors as spot color swatches in Adobe InDesign. Then, you can provide us a PDF and we can print each plate.
Using Riso inks to produce color photos is possible. Sometimes the results do not turn out great, but they can also be spectacular.
The simplest (and cheapest) method is simply to print your photograph in a single ink color.
If you want color photos, you can try simulate the effect by mixing or Red, Teal, and Purple Inks (comparable to Red/Green/Blue). You can also get creative and do wacky color combos.
Use this tool to play with your images: risoseparator.tools