Thinks to keep in mind when designing for letterpress
Taken from Boxcar Press
WIDTH OF LINES: Lines should be .25 point (or .003”) or thicker please! No hairlines!
FONTS: Letterpress excels at printing type and handles most fonts very well. We recommend using type no smaller than 6 point.
NUMBER OF INKS: letterpress printing traditionally uses 1 or 2 spot colors; 3 or 4 spot colors make for an extravagant and lavish production.
SCREENS: Letterpress excels at printing colors at 100%. If you’d like to incorporate a lighter color, we recommend using a second lighter ink color instead of a screen. Screens are more suited for offset printing, not letterpress.
REVERSE TYPE: Depending on the size of the reverse type, your reverses can clog up on the press. Because of this, we recommend a type size of 12 point or larger for reverse type, though this does vary depending on the typeface that you use. You may have to add a small stroke to the reverse type to compensate for letterpress ink gain. Also, if we're printing text and the solid area around your reverse type in the same color, we may need to print the solid area in a separate print run. Extra press runs do increase the cost of printing.
LIGHT INK ON DARK PAPER: With letterpress, we tend to print dark ink on light paper, because that is letterpress printing’s strength! Light ink on dark paper is really best suited for engraving. When a client wants to incorporate a darker color, we might suggest printing an offset flood on the back side of a light colored paper, or duplexing a dark colored paper to a light colored paper. That said, if you really want light ink on dark paper, just be prepared for paper show through. With letterpress, we use translucent inks. Printing light ink on dark paper will be like using a thin coat of white paint on a brown wall: you’ll see the brown color through the paint. If using a pure white ink or metallic ink, we can run a piece through the press twice, at an additional cost, to create a more dense color.
LARGE SOLIDS (large solids are areas larger than 0.7cm thick):Letterpress printed solids look different from offset printed solids. The paper tends to show through large solids, creating a slightly textured look that’s almost suede-like (we think this is a beautiful look by the way!). If you have a large solid and thin text in the same color, we’ll need to print the solid in a separate press run, to give the text a good deep impression and proper inking. Extra press runs do increase the cost of printing. Large solid areas can cause buckling of the paper, especially if using a thinner machine-made paper stock. You’ll also notice the depth of impression may appear less noticeable on really large letterpress solids—it doesn't have the contrast that line-art or type would have.