Printing blanket damage (often referred to as "blanket bruising" or "blanket pitting") is a serious issue that can lead to costly press downtime and a decline in print quality. Although there are many causes, such as improper blanket wrapping, excessive impression pressure, and blanket aging, the paper itself can sometimes be the root cause.
1. Hard Particles Embedded in or Adhering to the Paper Surface
This is the most common paper-related cause of printing blanket damage.
During the papermaking, processing, or handling process, impurities may become embedded or adhered to the paper surface. Common types include:
Sand and dust from the papermaking workshop environment
Metal debris from worn cutting or paper-cutting blades
Hard fiber clumps or undispersed pulp particles
Residual debris from tape, joints, or packaging
These hard particles, when passing through the printing impression area under high pressure, will directly press into the soft surface of the blanket, causing permanent indentations, pockmarks, or even holes, typically manifesting as small, scattered dot-like marks on the blanket.
✅ Preventive Measures: Using paper from mills with strict cleanliness control and equipping the finished product processing stage with magnetic separators and high-density screens can significantly reduce this risk.
2. Local Thickness Increase (Thick Spots)
Paper thickness cannot be perfectly uniform, but sudden and significant thickness fluctuations can impact the blanket like a punch.
For example:
Normal paper thickness: 0.10–0.12 mm
Paper roll joints (where two rolls are spliced) can reach 0.30–0.40 mm in thickness
Folded corners or creases can create sudden thickness protrusions
Under normal printing pressure (where the blanket is typically compressed by 0.10–0.15 mm), such thick spots can cause excessive local compression of the blanket, resulting in bruising. The damage usually appears as one or several large and deep pits rather than numerous small pockmarks.
✅ Preventive Measures: Properly handling paper roll joints (by beveling, flagging, or grinding flat) and precisely cutting the paper can prevent such problems.
3. Paper Curling or Wavy Edges Leading to Paper Feed Issues
In this case, the paper does not directly damage the blanket but causes blanket damage due to poor flatness, which leads to paper feed problems.
Mechanism:
Wavy edges or severe curling cause the paper to deviate and get stuck at the impression cylinder
Subsequent sheets overlap with the previous one
Multiple sheets accumulate in the impression area
The result is usually a large-scale crushing or tearing of the blanket rather than small pits, presenting as large, irregular damaged areas.
✅ Preventive Measures: Selecting paper with good humidity control and balanced winding tension (such as offset paper that has undergone proper temperature and humidity conditioning) can significantly reduce the risk of paper jams.
4. Coating Powder Shedding or Fiber Detachment
Some papers have insufficient surface strength, and during printing, the coating or surface fibers can peel off the paper and transfer to the blanket.
Initially, this forms ink and powder build-up - soft deposits. However, if the press continues to run without timely cleaning, the accumulation can:
Be compressed under repeated pressure
Harden due to heat or UV curing
Ultimately be pressed into the blanket, causing permanent damage
This type of damage usually develops gradually and is not caused by a single sheet of paper.
✅ Preventive Measures: Use paper with surface strength that meets standards (such as passing the wax stick test or IGT scuff resistance test) and regularly clean the blanket.
5. Important Note: Not All Blanket Damage Is Caused by Paper
As a responsible supplier, we also want to help our customers avoid misjudgment. Common non-paper causes of blanket damage include:
Excessive blanket wrapping
Excessive impression pressure
Aging of the blanket and loss of elasticity
Dry ink skins falling into the impression area
Dry ink or varnish clumps in the ink fountain
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