Wondering whether you can print on something without needing primer? Draw a line on the surface with this pen: if the ink beads up, your prints won't stick. Note: leaves a permanent mark, so test a spot you aren't using. We tried on a few different materials, and it seemed to agree with our testing.
Leaves a permanent mark — don't test on anything you can't afford to mark up. 38 dynes is a reasonable threshold but sources and inks may vary in their surface energy requirements. Pen provides no guarantee, but it's handy to have around.
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Last updated: March 27, 2026