Spray It On
When the ink has dried, spray on a light coat of polyurethane and let it dry according to the instructions on the can. This should be done outside on a still day (there should not be too heavy a breeze). Sand the surface again with 220-grit paper. "This should be a really gentle sanding, just to knock off any roughness," says Ossana. If you blow through the ink, just reapply to the raw areas. Then spray another coat of poly, a little heavier this time. Use even strokes and hold the can about 8-10 inches from the surface.