A few things to consider when designing for letterpress printing
Each color or impression requires its own run through the press. Each area of blind deboss, printing without ink, requires its own pass through the press.
Any area of solid ink larger than 1/4” sq. may print mottled. Floods of color are not recommended. Letterpress excels at nicely balanced line work. If you want an area to appear to have full coverage, consider using a halftone.
Point size of type should not dip below 8 pt in most cases. Some faces work better than others. I have found that thin san serif fonts can perform well if you are planning for very small letters.
Small letters spaced very close to one another may appear larger and may appear to be closer together when printed. Consider expanding your letter spacing.
Lines should not be any smaller than .25 pt. Some art brushes in vector drawing programs will not read differently / incorrectly. Please feel free to send me the illustration and I can help guide you.
Depending on your design, your one color design may require more than one pass through the press. For example, if your design has one area that is heavy with elements , and another area with very little else than one small element with lots of empty space surrounding it, it will be challenging to print both of these accurately with one run. Think of it as an island as illustrated by the doodle below.
All designs must be created in a CMYK environment and be 100% K. This means all black, and only black.
Create color separations either on separate file docs or on the same document . If submitting all separations on the same file, use one color for each separation. Magenta, cyan, and yellow.
If you want to read more about how to submit a file, Boxcar Press has a more detailed breakdown of the process here.