Top 10 Most Common Ink Problems
 
Having persistent problems using inks on your offset Press? Here's a quick reference guide for Print buyers, Plant Mangers and Press operators on how to resolve some of the most typical complaints:

Chalking - A condition that occurs when the ink is lacking proper varnish for the paper on which it is printed. * The dried ink film has no binding to the paper and will scuff off as a dry, chalky powder.

Causes:
1. Excessive vehicle or varnish penetration
2. Stock is too acidic
3. Stock is too absorbent
4. Fountain solution pH too low
5. Ink too soft, providing no hold-out

Solutions:
1. Add body gum or water-repellent varnish
2. Check pH of paper, avoid highly acidic coatings
3. Avoid highly absorbent paper-drains ink solvent-use inks with higher solids
4. Adjust fountain pH to higher level (4.5-5.5
5. Increase driers to speed drying before vehicle sets into stock
*Use gloss overprint varnish to save a job that's printed
 
 
Dot Gain - The halftone dots increase in size, causing the printed signature to lack sharpness.

Causes:
1. Too much pressure: from roller-to-plate, plate-to-blanket or blanket-to-blanket
2. Dots squashing at the point of impression
3. Blankets or rollers too soft
4. Fountain solution too acidic and conductivity too high
6. Running excessive amounts of ink

Solutions:
1. Check settings and correct to proper pressure
2. Make ink stiffer, use higher tack inks, or add heavy binding varnish
3. Recondition blankets or rollers; replace if necessary
4. Reduce amount of fountain solution concentrate and check water.
The pH should be between 4.5-5.5, and conductivity should not exceed 1500 micromhos
5. Consult with ink dealer for a more pigmented ink
 
 
Drying or Inadequate Drying -Printed ink film is wet or tacky for an unreasonable amount of time

Causes:
1. Ink is waterlogged
2. Ink film thickness is excessive
3. Stock is not porous enough or has high water content
4. Relative humidity is too high
5. Insufficient air/oxygen circulation

Solutions:
1. Make ink more water-resistant by adding heavy body varnish or water-repellent varnish and alcohol (15 percent)
2. Run less ink-increase the strength of ink
3. Switch stock to correct porosity or water content
4. Use a dehumidifier, use alcohol, and drying stimulator in the fountain solution, air condition plant
5. Wind, sheets-use minimal anti-offset spray. Nonporous plastics or foil should be kept in small lifts
 
 
Hickeys -Particles that result in spots or small dark areas on the printed sheets*

Causes:
1. Foreign particles
2. Plates particles
3. Dried ink particles
4. Loose paper coatings
5. Dampener cover particles

Solutions:
1. Check pressroom for dust, dirt, and spray powder
2. Check plates for loose coatings or shavings
3. Avoid dried skin when removing ink from cans or kits
4. Check and vacuum incoming paper. Adjust ink tack for poor paper coating strength
5. Replace suspect sleeves or rollers as needed *Properly maintained " hickey-picker" rollers do work to prevent this problem.
 
 
Ink/Water Balance -Frequent adjustments required on press to maintain print quality

Causes:
1. Excessive fountain solution
2. Fountain solution too strong
3. Fountain solution too weak
4. Ink taking up too much water
5. Improper dampening roller setting

Solutions:
1. Reduce dampener settings-increase amount of isopropyl alcohol or alcohol replacement
2. Decrease fountain concentrate-adjust pH to a 4.5-5.0 range
3. Increase fountain concentrate in the solution-bring pH to 4.0-4.5 range. Add gum arabic to solution
4. Add water-repellent varnish to the ink
5. Reset rollers-be sure dampener form rollers are driven by the vibrator roller and not the plate.
     Check durometer of rubber transfer rollers.
 
 
Picking/Linting-Picking refers to the lifting of the coating on coated stocks onto blankets, plates, and rollers. Linting refers to the pulling of fibers on uncoated stocks.

Causes:
1. Insufficient ink on rollers
2. Too much water reaching paper
3. Ink too tacky for the paper
4. Pressure set too high for ink/stock combination being used
5. Blanket too tacky

Solutions:
1. Reduce ink strength and increase ink flow across rollers to maintain ink density
2. Reduce dampener setting for proper performance
3. Reduce ink's tack with proper reducer or solvent, increase ink film thickness
4. Reduce impression pressure, repack to manufacturer specifications
5. Consult blanket manufacturer. Treat blanket or change to a less tacky blanket. Check blanket wash.
 
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