There are many variables that go into creating the perfect printed product. Here’s a list of some common paper-related printing problems along with some probable causes and solutions.

 

Mottle

Description
Ink takes unevenly on the sheet and varies in large or small irregular patches. This occurs most often in large solid areas and especially in dark tones.

Probable Causes

  • Uneven ink absorption 
  • Poor sheet formation 
  • Worn plate
  • Worn blankets 
  • Low blanket packing 
  • Low print pressure 
  • Water interference  

Solutions

  • Try different ink or print on reverse side 
  • Change color sequence and print mottled color last 
  • Decrease dampening and print mottled color first 
  • Change plates 
  • Change blankets (quick release blankets may minimize) 
  • Add more packing 
  • Run a different lot of paper for comparison

Dusting

Description
Coating dust or filler in uncoated paper builds on the blanket and in the non-image area, causing premature plate wear. (High filler content sheets are more susceptible).

Probable Causes

  • Insufficient bonding between base sheet and coating 
  • Plate being run too dry (inadequate fountain solution)

Solutions

  • If there is a spare unit on the press, use it to print blind without water 
  • Increase dampening

Delamination

Description
Paper peeling apart or separating from within.

Probable Causes

  • If the internal bond of the paper cannot withstand the tack of the ink or other printing forces, the sheet will delaminate.

Solutions

  • Reduce ink tack 
  • Replace paper

Linting

Description
Fiber build-up of an uncoated paper; fibers are pulled from the surface.

Probable Causes

  • Paper is either not properly surface-sized or contains too much filler 
  • Ink too tacky 
  • Too little dampening 
  • Press speed too high

Solutions

  • Use surface-sized paper 
  • Reduce ink tack
  • Reduce printing speed 
  • Increase dampening

Picking

Description
Lifting of coating onto blankets, plates, or rollers, causing a rupturing of the paper surface. (Pickouts foreign material within the fibers originating from contaminated pulp or during manufacturing.)

Probable Causes

  • Ink too tacky 
  • Internal bonding of paper fibers or bonding of the coating not strong enough to withstand the pull of the inked blanket

Solutions

  • Reduce ink tack 
  • Reduce press speed 
  • Reduce pressure 
  • Change to less tacky blanket 
  • Use short-grain paper when it only goes through the press once 
  • Consult paper supplier to assess paper quality

Piling

Description
Accumulation of ink and/or paper material on the rollers, plate, or blanket during printing.

Probable Causes

  • Unstable ink with pigmentation that is too high 
  • Waterlogged ink—causes pigment to separate due to insufficient viscosity and tack 
  • Underpacked or poorly conditioned blanket

Solutions

  • Run less water on the press 
  • Consult ink manufacturer for ink reformulation (varnish may be added) 
  • Clean and condition rollers and/or blankets 
  • Check roller settings and blanket packing

Wrinkling

Description
Paper wrinkles as it passes through the press.

Probable Causes

  • Paper has wavy or tight edges 
  • Paper has a curl 
  • Uneven blanket 
  • Pressure too high 
  • Press speed too high 
  • Paper being run short grain 
  • Paper cut from unlevel reel and has chain or baggy marks

Solutions

  • Adjust feeder and grippers 
  • Reduce speed 
  • Reduce print pressure 
  • Change the blanket 
  • Change grain direction 
  • Consult paper supplier—paper may be the cause

Static Electricity

Description
Sheets stick together, resulting in poor control during feeding and delivery.

Probable Causes

  • Pressroom too dry 
  • Paper too dry

Solutions

  • Use humidifier or static eliminator

Blanket Smashes

Description
A compressed area on a blanket due to excessive pressure.

Probable Causes

  • Scuffs—a roll up on paper, usually originating at the edge of a sheet 
  • Scraps—paper trimmings, folder sheets, labels, packaging materials, etc. 
  • Splices in cartons or skids 
  • Folded edges

Solutions

  • Prevention 
  • Top and bottom sheets in a carton should be examined carefully because they are most susceptible to damage 
  • When loading the press, examine sides of lifts 
  • Replace blanket

Paper News

04/08/2014
Paper Matters - Volume 8, Number 2

Read more paper news

 

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