Clean before you blame the ink
Most aluminum print failures start with contamination: machining oil, fingerprints, adhesive from the protective film, dust, or an invisible mill lacquer. Wipe with isopropyl alcohol (or the cleaner your ink and primer vendor specifies), keep bare hands off the print area, and let the surface dry fully before priming or printing. If the sheet arrived film-covered, remove the film and clean again — residue loves to hide under the edges.
White underbase decides opacity
CMYK alone on reflective aluminum lets the metal show through, which can look intentional for a tinted metallic logo. For solid brand colors, lay white first, then color. The artwork needs a separate white channel that matches the color art. Oversized white creates a halo; undersized white leaves a shiny fringe. Test the full white-plus-color stack — white increases film build and can change how the print flexes at edges.
Cross-hatch tape testing is not optional
UV ink sits on top of metal; it does not soak in like some solvent systems. Print a small coupon on the exact finish, cure it the way production will, cut a cross-hatch, and pull with the tape your shop standard uses. Ideal result: ink lifts only inside the cut lines. Broad peel means change primer, ink, cure, or substrate — do not scale a failing coupon into a wall of panels. Vendor guides from major UV platforms emphasize the same sequence: clean, print, cure, tape-test, then decide on promoter.
Clear coat and handling
Some outdoor or high-abrasion installs get a clear UV varnish for extra scuff resistance. That is another layer to qualify — varnish on poorly adhered color just makes a thicker flake. Edge wear on aluminum signs often shows first at corners and fastener holes; design margins and mounting so fingers and tools are not scraping the graphic during install. Shipping and crating notes for large panels live on our shipping and crating guide.
