What causes color variation? The most common reasons include changes in paper batches or ink batches, fluctuations in printing pressure, and color shifts occurring before and after lamination. Controlling color variation relies on a color-matching workflow: adjusting colors before the actual print run, producing proofs, checking them under a standard light source, and obtaining approval before proceeding to the main press.
What is registration? In multi-color printing, patterns of different colors must align perfectly. Poor registration leads to issues like edge ghosting, white gaps (misalignment revealing the substrate), or color overlap errors. Registration accuracy depends on the press’s performance and operator skill; the more stable the machine and precise the calibration, the cleaner the registration.
Color matching requires the right light source. It must be performed under standard lighting conditions—such as D50 or D65, which are industry standards simulating natural daylight and average daylight. Matching colors under ordinary lighting will never yield accurate results. Professional print shops use standard light boxes, and you can request to inspect colors under standard lighting during acceptance.
What is color accuracy? It refers to the consistency between the printed output and the design draft or signed proof. Deviations can cause a brand’s signature red to shift to orange-red, or a metallic gold spot color to turn into a brassy yellow. Color accuracy is influenced by factors such as paper whiteness, ink batches, printing pressure, and ambient humidity, making it the most difficult aspect of printing to stabilize.
Ultimately, color management is about standards. If the light source, signed proof, and retained sample are all correct, color variation is minimized; if standards are vague, consistent color matching is impossible.
When printed colors are off or patterns show ghosting, the problem usually lies in one of two areas: registration or color accuracy. These are the details most easily overlooked in packaging printing, yet they have the biggest impact on final acceptance. Understanding these concepts ensures you are well-prepared for the inspection process.
Signed proofs and retained samples are crucial. The “signed proof” is the printed sample approved by the client, serving as the color benchmark for the bulk run. “Retained samples” (including the signed proof and the first piece off the press) are kept for comparison should issues arise with the bulk order. Signing a proof is not merely a procedural step; it establishes the anchor point for quality standards and should always be confirmed in person.
How should inspection be conducted? Focus on three key areas: color consistency with the signed proof, clean registration without ghosting, and crisp halftone dots without blurring. The sampling ratio is determined by the order size, and any issues found should be documented on the spot. Only when print quality standards are incorporated into the contract is there a basis for acceptance.
