Ink & Substrate Interaction Flashcards
7 cards from real GMI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Ink & Substrate Interaction flashcards as text
The Parker Print Surf (PPS) value of a substrate is a measurement of its:
Answer: Surface roughness expressed in micrometers
PPS value measures the air-leak roughness of a substrate surface in micrometers, with lower values indicating smoother surfaces that produce higher print quality.
Ink ghosting in offset printing can be caused by which ink-substrate interaction?
Answer: Ink starvation on press rollers causing locally depleted ink film on repeat images
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.
Which of the following substrate characteristics is measured using a Cobb test?
Answer: Water absorption of paper over a specific time period
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.
In waterless offset printing, the ink-substrate interaction differs from conventional offset primarily because:
Answer: No dampening solution is used, so ink selection and substrate surface energy are managed entirely through silicone plate coatings and temperature control
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.
The phenomenon of 'fiber piling' on the blanket during offset printing is caused by:
Answer: Ink tack exceeding the surface bonding strength of substrate fibers, pulling them off during impression
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.
In GMI print standardization, the relationship between Total Area Coverage (TAC) limits and substrate type is important because:
Answer: Higher TAC values on absorbent substrates can cause excessive ink penetration, drying problems, and substrate distortion
On absorbent substrates, excessively high TAC causes the ink vehicle to over-penetrate, leading to slow drying, ink spread, and mechanical distortion of the substrate from excessive wetting.
When evaluating ink adhesion on a finished printed substrate using a tape pull test, a result showing ink transferring to the tape indicates:
Answer: Ink adhesion to the substrate is insufficient and may not meet durability specifications
Ink transferring to the tape in a pull test means the adhesive bond between the ink and substrate is weaker than the tape's pull force, indicating the printed product will fail adhesion durability requirements.