Mineral Pigment Morphology Effects on Capillary Pressure and Vehicle Separation
Mineral pigment shape dictates coating pore diameter, where narrow platelet networks accelerate ink vehicle separation and induce print chalking.
Blanket Piling
Surface Accumulation
Deposition of loose debris or paper coating particles on an offset printing blanket causes a loss of ink transfer and image clarity. This process, known as blanket piling, is caused by weak surface strength or excessive dust on the paper edges. The accumulated material absorbs moisture and ink, which leads to a loss of print density.
When the accumulation builds up in image areas, it creates a textured surface that prevents smooth ink laydown and results in hickeys or void areas. This issue happens primarily in lithographic printing because of the dampening solution, which can soften the paper coating binders and cause them to lift off under the tack of the ink.
Moisture Sensitivity
Water-soluble binders in the paper coating can become tacky when they absorb dampening solution on the blanket. As a result, blanket piling occurs when the paper’s coating cannot withstand the combination of water and high tack forces. The softened coating is stripped from the paper surface and remains on the blanket.
Correcting the moisture resistance of the paper coating helps eliminate this build-up.
Operational Control
Preventative maintenance is required to keep the offset blanket clean during long print runs. Frequent wash-ups are necessary to remove the piled material and restore ink transfer. This action increases both the paper waste and the production time of the print run.