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

PPS value measures the air-leak roughness of a substrate surface in micrometers, with lower values indicating smoother surfaces that produce higher print quality.

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

Mechanical ghosting occurs when ink rollers are not replenished fast enough between impressions, causing a ghost image from ink depletion to appear on subsequent printed areas.

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

The Cobb test (ISO 535) measures the mass of water absorbed by one square meter of paper under defined conditions over a specific time, typically 60 seconds.

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 offset eliminates the dampening solution, using silicone-coated plates and precise temperature control to define ink-repellent non-image areas, making ink formulation and substrate compatibility critical.

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

Fiber piling occurs when ink tack is high enough to pull loosely bonded surface fibers from the substrate, which accumulate on the blanket and degrade print quality over a press run.

(GMI) Graphic Measures International Certification Practice Test

(GMI) Graphic Measures International Certification Practice Test

GMI Ink & Substrate Interaction 3