Ink & Substrate Interaction Flashcards

How does increased substrate moisture content typically affect ink drying time in heatset web offset printing?

Answer: It extends drying time because moisture competes with solvent evaporation in the dryer

Higher substrate moisture content increases the energy load on the dryer and interferes with solvent evaporation, extending the time required for complete ink drying.

When printing UV-curable inks on non-porous substrates such as plastics, which property is most critical for ink adhesion?

Answer: Substrate surface energy being sufficient to promote wetting

UV inks on non-porous substrates rely entirely on surface energy for wetting and adhesion since there is no absorption mechanism; insufficient surface energy leads to adhesion failure.

Dot gain on an uncoated substrate compared to a coated substrate of the same nominal stock weight is generally:

Answer: Higher, because ink spreads more in the porous uncoated surface

Uncoated substrates have open porous surfaces that allow ink to spread laterally as it penetrates, significantly increasing physical and optical dot gain compared to coated stocks.

In printing, 'show-through' and 'strike-through' differ in that:

Answer: Show-through is the visibility of printing from the reverse side, while strike-through is complete ink penetration through the substrate

Show-through is the optical phenomenon of seeing print from the opposite side due to low substrate opacity, while strike-through is actual physical penetration of the ink through the substrate.

Which ink sequence principle is applied in multicolor offset printing to optimize wet trapping?

Answer: Print inks in decreasing tack order so each subsequent ink has lower tack than the previous

Printing in decreasing tack order ensures each subsequent wet ink transfers properly to the previous ink layer, as lower-tack ink can adhere to higher-tack ink without splitting issues.

Static electricity in substrates during printing is most problematic because it:

Answer: Causes sheets to stick together and misregister, disrupting sheet travel and feeding

Static charge causes substrates to cling to each other or to press components, leading to feeding failures, double sheets, and registration problems during printing.

Paper whiteness and paper brightness are different measurements because:

Answer: Brightness measures the spectral uniformity across the visible range, while whiteness only measures a single UV wavelength

Brightness (ISO 2470) measures blue-light reflectance at 457nm and includes fluorescent whitening agent response, while whiteness (CIE whiteness) evaluates spectral uniformity across the full visible spectrum.