Letterpress Goes 3D: Preparing a Born-Digital Image for Wood Engraving Using Photoshop and Illustrator

This tutorial will show you how to convert a digital image into a vector image that can then be laser cut to create a wooden letterpress block for printing. Essentially, this guide will take you from digital image to woodcut!

Before you begin, it is important to ensure that the image you select can be easily converted to pure black and white, if it isn’t purely black and white already, as letterpress can only print one color at a time. It is also important that the image is not overly detailed, as both Illustrator’s trace function and the laser cutter laser have a limited level of fidelity — though not extremely low. Avoid things like stippling, crosshatching, and detailed shading, for instance.

Note that you can also use this method to create woodcut engravings of hand-drawn images! Make sure your drawing is done with black ink or solid pencil on white paper, has relatively thick lines, and does not contain shading or tiny details. You may achieve best results with hand-drawn images when skipping steps 4 and 5. See the forthcoming hand-drawn images guide for more.

Finally, the process for replicating historical images is often a bit more complicated, as clean-up is often required to get a clean vector or model for printing. Therefore, if you are looking to replicate a historical image, please use the guide made specifically for that purpose.

If you would like to follow this guide in video form, a video walkthrough is available below!

  1. If the image is from a print source, scan the image you intend to create a laser cut of. If it is a digital source, save the image.

2. Save the scanned image as a PNG or other hi-res image file.

3. Oftentimes, the image file will include some extraneous details as well. In Photoshop, extraneous details (text, etc.) can be cropped away if they are outside the image using the crop tool on the left side toolbar.

4. If necessary, convert the full image to either 100% black or 100% white if it is not already. To do so, in Photoshop with the image selected, go to Image > Adjustments > Black and White. 

5. In the menu that opens up, set each color slider all the way to the right (where it will be white on the color slider bar). This will convert all non-black color to pure white.

6. Invert the color of the image. The laser cutter prints in relief — this means that the black portions of the image will be cut by the laser cutter, and the white portions will remain raised. The raised portions of the laser cut engraving will take on ink when used for letterpress printing, ultimately creating the image on the paper. Invert the image’s color to ensure the right parts of the image are cut and printed.

7. Crop the image further. Cropping at this stage will help set the eventual size of the woodcut block. You want to have thin empty margins around your image to account for some spacing on the wood block. If your image is centered, as in the example, you can adjust the canvas size on the left in order to crop it down while keeping it centered.

8. Create a mirror image by going to Image > Image Rotation > Flip Canvas Horizontal. A mirror image will ensure that your letterpress prints come out properly.

9. Export the image as a PNG or JPEG.

10. Now, open Adobe Illustrator. You will now trace the image so it may be “seen” by the laser cutter.

11. Create a new 18 x 24 inch Illustrator file. The laser cutter bay is 18 inches tall and 24 inches wide, so this will ensure that your image is to scale. However, during this process, avoid using more than 7 inches of vertical space, as that is the size of the wood the laser cutter uses; while your file should be 18 x 14 inches, you should only use up to 7 x 24 inches of space.

12. Place the image on the document by navigating to File > Place.

13. Navigate to Object > Image Trace > Make.

14. This will create a basic trace. To tweak the tracing, go to the right column. There are multiple presets available, but the one that will give you the highest quality trace is typically “High Fidelity Photo.”

15. With a preset selected, click the menu button next to it, the box with white lines in it.

16. A menu will open up. Adjust sliders and setting in order to generate a tracing as similar to the initial image as possible. This process is generally one with a lot of tweaking and trial and error.

17. Ensure that the “mode” option in this menu is set to “Black and White.” Even if the image appears to be fully black and white, there may be shades of gray that need to be resolved to pure black so that laser cutting can occur.

18. When done, click “expand” in the right hand column. This will finalize the trace.

19. You will now have a pure, solidly blocked, black and white image. Resize the image to the desired size – 1 inch equals 72 pt font – using transform in the top right corner.

20. Move the image to the top left corner of the artboard.

20a. If your image is white up to its edge (in other words, if when letterpress printed, it will be black/inked to the edge of the block), it’s important to indicate where the edges of the block are for when the design will be sawed out of the sheet of wood it is engraved on. You can do this by drawing black rectangles along the edges of the image, using the blue lines that appear when you select the image as a guideline. These black rectangles will be engraved by the laser cutter, providing a clear indicator of where the block needs to be sawed off from the larger piece of wood. See the below image.

21. When your design is complete, save the image as an Illustrator Legacy file by navigating to Save As > Illustrator and selecting “Legacy” from the drop down menu that will appear in a pop-up menu after clicking the Illustrator option. This file type is readable by the laser cutter hardware. Your file is now ready to be cut!

Now you have a vector image file ready for engraving wood in a laser cutter. Your next steps may vary depending on your situation, but Northeastern Huskiana affiliates can reach out to the CAMD Makerspace with their file ready to request to make a laser engraving.

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