Create press-ready artwork for screen printing

Introduction

Prepare your artwork.
If you're using your own artwork, it should be in vector form (Adobe Illustrator) and be four colors or less.
Download working files.

If you'd like to follow along with the files we're using in the video demonstrations, you can download the artwork and linked files in the attached zip file.
Select your file prep method.

Note that the video lessons include two different options for separating, trapping, and halftoning your files.

The 'Fun' poster uses the pathfinder method while 'San Francisco' uses a manual method.

Feel free to try both methods but it's only necessary to follow one method or the other, depending on what works best for your artwork.

Textures

Photograph your own textures.
For the purposes of our example, you can photograph the sky and the street, but if you're working with your own design, feel free to get creative and photograph wood grain, brick, foliage, or whatever texture might work best for your artwork.
Refine your texture image in photoshop.

Bring your texture photo into Photoshop, crop to your desired size, and use the stamp tool to remove any specific objects in the photo that might jump out at you. Tip: use a soft brush to make the stamp tool's path less noticeable.
Download texture source images.

If you'd like, you can also work from the example source images we use in the videos.
Convert image to grayscale and adjust levels.

We find that higher contrast textures typically work best to enhance our artwork.
Resize and save the photo as a TIFF.
If this texture will be used across your entire poster, change the image size and resample up to the size of your poster (24" x 18" in our example) at 300 dpi.
'Place' texture file in Illustrator.
You now have the ability to change the color of your grayscale tiff file in Illustrator and stretch the texture if needed to fit the context of your poster artwork.

You can also go back to your texture in Photoshop, make adjustments, and they'll automatically update in Illustrator.
Create a white cloud texture.

Follow the steps in videos 2 and 3 to create a light colored textured on a dark background. This requires a bit more work than a dark background on a light surface, but provides great results when adding textures like clouds, smoke, and dust.
Recolor textures to match artwork.

You can adjust your white textures in Photoshop to match an off-white paper color or experiment with different colors until you acheive the desired results. Remember, your texture color should match either your paper color or one of the ink colors you'll be printing.

Color Separations

Prepare your file for separation.

Make sure your file is using a limited color palette, outline strokes, and expand filters.
Make sure separations stay consistent and aligned.
Combine your artwork into one layer and copy that layer to create your first color separation. For the proceeding separation use the same original layer. This will ensure your artwork stays consistent and aligned throughout each separation.
Stay organized with color.

Use your swatches to select each color individually. For colors that are not being separated simply change their color to white, leaving only the color you'd like to separate. Remember, in the San Francisco poster, brown represents both colors overprinting, so be sure to include it in both separations. Also, don't forget to not only change the color of solid fills but to also change the colors in gradients and certain effects such as "inner glows" as well as linked textures.
Check your work and make revisions.
Once you have your colors separated, make sure to layer each color in the order you plan to have them printed. Play around with making each layer semi transparent to double-check your work. If something doesn't line up correctly you can always go into each individual layer and make adjustments. You can also pull from your original artwork layer if needed.

Trapping

Prepare your artwork for trapping.

Use the pathfinder tool to cut out the background including any areas that will be showing through to the paper color. This will allow you to apply trapping and quickly mask off the areas where no trapping is needed.
Manual trapping - consider which parts of your artwork to trap.

Carefully examine your artwork to decide what areas you would like to trap. Consider the transparency/opaqueness of each ink layer and how they will conceal or reveal the layer(s) underneath them. Butt registration can be used to the artwork's benefit, so it's not absolutely necessary to trap everything, especially when dealing with overprinting.
Save each trapped layer as a new file.

Saving each layer as a new file will ensure redundancy so you can always revisit your original file to make adjustments.

Halftones

Convert each layer to solid black fills.

In each layer, select the corresponding color swatch and change that color to black. The same goes for anything that is not a solid fill such as gradients, effects and textures. Eventually you should be left with a completely black and white file. Remember that it's not as simple as grayscaling your artwork. For instance, grayscaling teal would end up creating a gray tone. In this process every ink color as a pure solid fill represented as pure solid black. In other words teal at a 50% opacity will now be manually converted to a black at a 50% opacity.
Prepare each layer for bitmapping.

Save each black and white layer as an individual file, and be sure to delete any hidden layers within those files to make them smaller and thus faster to rasterize in photoshop.
Halftone each layer in Photoshop.

Drop each layer into Photoshop following the settings in the video. Grayscale and bitmap each layer using the specific halftoning techniques described in the video. Remember to choose the correct halftone angle for each layer.
Test your work.

Once each layer has been saved as a single bitmapped/halftoned TIFF, place each file into a new illustrator file and change its colors to match your design. Export this file as a jpeg to test your work.
Export transparent objects using artboards in settings (Fun Poster)

When you export the transparent objects for halftoning, be sure to export with "use artboards" selected. This way you'll be able to easily place the halftoned file back into Illustrator and simply align it to the artboard for perfect placement.

Ian Jepson

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