Problems

Problems

Cause

Action
  • SLURRING
    Image distortion or dot smearing, Particularly in the shadow areas

 

 

 

 

 

  • Horizontal bands in the print
  • Incorrect plate and blanket packing relationship
  • Check and correct packing whare necessery
  • Too much back cylender pressure when printing on costed paper
  • Run with minimum pressure
  • Running too much ink or coated paper
  • Reduce ink feed
  • Blanket tension insufficient
  • Tighten Blanket correctly.
  • Piling of paper coating on printing areas of the blanket.
  • Try a fountain solution containing a wetting agent.
  • Loose and /or slipping blanket
  • Check blanket and packings are correct.

 

Problems

Cause

Action
  • Stripping : Inking roller taking damp instead of ink.

  • Inking rollers glazed or contaminated with solvents etc.
  • Carry out a complete wash up and /or use a deglazing product.
  • Solvent, surfactants or detergents retained in the dampeners after cleaning.
  • Ensure dampeners are thoroughly cleaned and rinsed.

Problems

Cause

Action
  • Cracking or Splitting

  • Plate Loose on cylinder
  • Clean lock-up mechanism, check that the plate is fitted properly and check that the plate is bent correctly.
  • Plate incorrectly fitted
  • Refit Plate
  • Plate packing has 'crept' on cylinder.
  • Remount Plate
  • Fountain Solution and ink not compatible
  • Change Ink or fountain solution.
  • Fountain Solution extracting an ink emulsifying agent from the paper coating
  • Stiffen Ink with varnish.
  • Avoid Fountain solutions containing 'wetting' agents.
  • Try another paper.
  • Emulsification of the Ink
  • Stiffen ink with varnish. Run less water.
  • Check with conductivity meter.
  • Change ink and run less water.
  • Solvents or surfactants held in the inking rollers after wash up.
  • Change 'wash-up' solution to a water miscible one and use a little water after using the wash-up solution.
  • Solvents or surfactants held in the inking rollers after wash up.
  • Ensure dampeners are throughly rinsed with water after cleaning.
  • Dampeners badly set
  • Reset paying particular attention to the plate dampener to reciprocator contact.
  • Glazed and/or wrongly set inking rollers
  • Deglaze or change rollers and re-set.
  • Plate being fogged prior to development. (neg.)
  • Try 'mild' etch otherwise make a new plate.

Problems

Cause

Action
  • Image Binding Image not taking ink or 'walks off'

  • Thick gum film on image
  • Remove the gum with warm/hot water, then use General Purpose Plate Cleaner. Ensure that the gum is buffed down to a thin film after application.
  • Solvents or detergents in fountain solution, dampeners, sponge or water bucket.
  • Ensure dampeners are properly rinsed after cleaning.
  • Avoid wash-up solutions dripping into water system.
  • Keep the sponge and water bucket clean.
  • Excessive fountain concentrate, or acid in fount
  • Make a fresh fount if necessary, using the conductivity meter. Reduce concentration by 50%.
  • Excessive alcohol being used
  • Reduce the alcohol content if possible.
  • Wrong Finisher/gum used.
  • Consult manufacturer's product leaflet.
  • Ink not feeding image (possible emulsification on start-up) Lack of water resistence.
  • Consult ink manufactuere
  • Plate to Blanket pressure too great (Possible swollen or embossed blanket)
  • Correct the pressure setting or if blanket is embossed change it.

Problems

Cause

Action
  • Dot Gain Image on plate greater than on film.

  • Over exposure of negative plate
  • Check exposure using sensitivity guide and product leaflet.
  • Poor film/plate contact on negative plate.
  • Check stripping technique, and that emulsion on the film is face down.
  • Under Development
  • Check manufacturer's instructions
  • Soft dot negatives allowing light to penetrate the edges of the dot.
  • Use contact Negatives.
  • Veiled Positives
  • Checks clear film for opacity and also dot shape.

Problems

Cause

Action
  • Dot Loss Image on plate is less or sharper than on film.

  • Over Exposure on positive plates. · Under Exposure on negative plates
  • Check exposure using sensitivity guide and product leaflet.
  • Poor film to plate contact on positive plates.
  • Check and/or improve stripping method.
  • Too much white light in plate room (positive plates)
  • Reduce the stray white light to a minimum.
  • Over Development
  • Maximum 2 minutes for negative plate, 5 minutes for positive.

Problems

Cause

Action
  • Plate Ware

  • Abrasive paper dust
  • Clean blanket more frequently if possible.
  • Badly milled ink.
  • Inform ink suppliers
  • Plate / blanket over packed
  • Check packings
  • Badly set inking rollers
  • Reset inkers to press specifications.

Problems

Cause

Action
  • Scumming Non - image areas becoming sensitive

  • Dirty or worn dampener cover.
  • · Clean or re-cover dampeners.
  • Plate incorrectly desensitised when made
  • · Use washout/storage gum, then try.
  • Insufficient development
  • Delete a small area in the background then run the plate. If this stays clean it would indicate insufficient development or bench contamination. Re-make the plate to manufacturer's instruction.
  • 'Ink Stick' (sometimes incorrectly called oxidation) Small spots of ink all over the plate on start - up, plate is drying out, and picking up ink from the dampeners.
  • Check for draughts across the press. · Use a fountain solution containing 'wetting agent' · Check with conductivity meter.
  • Ink too soft or greasy
 · Stiffen the ink with strong varnish. · Try a different ink manufacturer
  • Abrasive particles in the ink
  • Have the ink re-ground or replace with a better ink.
  • Abrasive particles in the paper
  • Reduce plate-to-blanket and back - cylinder pressure to minimum.
  • Half tones run with too much ink.
  • Run the link as stiff and spare as possible.
  • Slurring of half-tones
  • Reduce ink feed and reduce plate to blanket and back - cylinder pressure to a minium.

Problems

Cause

Action
  • Image Wear Premature image breakdown

  • · Under - exposure (neg plates)
  • Check exposure using sensitivity guide and product leaflet.
  • Plate exposed to white light before or during development (positive plates)
  • Follow manufacturer's instructions and develop under yellow light.
  • Fountain Solution too acidic
  • Check with pH and / or dosage. Change to less acidic fount.
  • Excessive plate/blanket pressure or roller settings on plate.
  • Check press setting or set to a minimum.
  • Swollen or embossed
  • Wash blanket and thoroughly dry. Reset the blanket.
  • Abrasive paper dust on blanket
  • Wash blanket and thoroughly dry. Reset the blanket.
  • Insufficient ink on image.
  • Run normal ink weight to lubricate and protect the image from wear.
  • Alkaline plate cleaner or incompatible solvent contained in plate cleaner, blanket wash etc.
  • Use Nulith Pressroom chemicals which are compatible with Nulith Plates.

Problems

Cause

Action
  • Scumming Plate tends to scum after about 10 - 20000 impressions.

 

  • Scum streaks appearing around the cylinder.

 

 

 

 

 

  • Scum streaks appearing across the cylinder.
  • Insufficient acid and or gum in the fountain solution.
  • Make sure the fountain solution is between 1 - 2%. Checking the pH is not enough as in some cases buffered founts may have been used. Check with conductivity.
  • Dirty or Worn dampener/s or ductor roller covers.
  • Wash or replace them.
  • Greasy fountain roller or greasy distributing roller.
  • Wash with spirit to remove grease, then desensitise with gum.
  • Uneven dampener setting against plate or oscillating roller.
  • Reset dampeners, checking for even pressure from end - to -end, and that the eccentrics are in the same directions.
  • Bouncing dampener rollers set too hard to the plate.
  • Reset dampener rollers.
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