GMI Ink & Substrate Interaction 3

Question 1

The Parker Print Surf (PPS) value of a substrate is a measurement of its:

Accepted Answer

Surface roughness expressed in micrometers

Answer

Surface energy in dynes per centimeter

Answer

Ink absorption capacity per unit area

Answer

Opacity percentage under diffuse illumination

Question 2

Ink ghosting in offset printing can be caused by which ink-substrate interaction?

Accepted Answer

Ink starvation on press rollers causing locally depleted ink film on repeat images

Answer

Ink absorbing unevenly due to variable substrate caliper

Answer

Excessive surface energy on the substrate attracting ink from non-image areas

Answer

Substrate fiber orientation causing directional ink flow differences

Question 3

Which of the following substrate characteristics is measured using a Cobb test?

Accepted Answer

Water absorption of paper over a specific time period

Answer

Surface roughness of coated paper

Answer

Ink holdout on the paper surface

Answer

Tensile strength of paper fibers

Question 4

In waterless offset printing, the ink-substrate interaction differs from conventional offset primarily because:

Accepted Answer

No dampening solution is used, so ink selection and substrate surface energy are managed entirely through silicone plate coatings and temperature control

Answer

Waterless inks have much lower viscosity, penetrating substrates more rapidly

Answer

Waterless printing requires substrates with higher moisture content to function correctly

Answer

Waterless inks require UV curing and only work on non-porous synthetic substrates

Question 5

The phenomenon of 'fiber piling' on the blanket during offset printing is caused by:

Accepted Answer

Ink tack exceeding the surface bonding strength of substrate fibers, pulling them off during impression

Answer

Excess dampening solution softening and loosening surface fibers from the substrate

Answer

Static electricity attracting loose paper dust to the rubber blanket surface

Answer

UV ink reacting chemically with uncoated paper fibers, causing them to swell and detach

Question 6

In GMI print standardization, the relationship between Total Area Coverage (TAC) limits and substrate type is important because:

Accepted Answer

Higher TAC values on absorbent substrates can cause excessive ink penetration, drying problems, and substrate distortion

Answer

TAC limits are fixed at 340% regardless of substrate type per ISO 12647

Answer

TAC limits only apply to digital printing processes, not offset

Answer

Lower TAC limits are required for coated stocks because clay coatings block ink absorption

Question 7

When evaluating ink adhesion on a finished printed substrate using a tape pull test, a result showing ink transferring to the tape indicates:

Accepted Answer

Ink adhesion to the substrate is insufficient and may not meet durability specifications

Answer

The ink has excellent cohesive strength but poor adhesive bond to the substrate

Answer

Adequate drying has occurred and the ink film is flexible

Answer

The substrate has excessive porosity that prevented proper ink anchoring