Category Archives: Sheetfed Inks

Poor Trapping – Process Inks

Ink/water is not in balance

Achieve and maintain proper ink/water balance Running a minimum amount of ink and water is always preferable

Ink film thickness may be wrong

Check that inks are running at correct density levels

Paper may have low absorption capacity

The lower the absorption of the paper, the slower the inks will set leading to less efficient trapping

Poor Transfer of Ink

Rollers are improperly or inadequately cleaned and glazed

Thoroughly clean rollers with a good quality glaze remover. After removing all ink with wash-up solvent, then apply hot water to rollers. This will remove gum glaze that is not soluble in standard solvent based wash-ups

Calcium build-up on roller surfaces

After normal wash-up, follow with a hot water / white vinegar wash (2:1) to remove calcium deposits

Rollers are improperly set or are swollen or distorted

Adjust roller settings or check roller surface condition

Indiscriminate use of wetting agents; gum and gum substitutes in fountain solution

Control use of fountain solution and additives which can have adverse effects on the rollers

Roller temperatures not warm enough

Make sure form rollers are 72°-80°F (22°-26°C) for optimum performance

Tinting / Toning / Scumming

Fountain solution condition

Check condition of fountain solution. If dirty and old, replenish with fresh at recommended dosages and correct temperature

Roller durometer or roller settings are out of specification

Check roller durometers and settings according to press manufacture’s recommendations

Too much pressure exists between plate and blanket

Check and correct if necessary

Temp of roller train and water pan

Form rollers should be close to 75°F (23°C) and water pan 65°F (18°C)

Improperly over packed cylinders – too much squeeze

Correct packing and re-torque blanket to press manufacturer’s specifications

Ink or dampener rollers are set too tight

Check and reset rollers to press manufacturer’s specifications

Blanket is glazed

Remove glaze or change blanket

Fountain solution is out of balance

Drain pans and tanks. Refill with fresh fountain solution at correct pH, conductivity, and Brix level

Prolonged use of oily wash-up solution

Change to fresh wash-up solution

Roller train temperature is too hot

Maintain forms at 72°-80°F (22°-26°C) surface temperature

Fountain solution is too hot in pans

Maintain fountain solution temperature in press pans at 65°F (18°C)

Ink roller durometers are either too soft or too hard

Check durometer, setting, and condition of ink rollers

Stripping

Rollers too hard and out of specification

Check durometers and replace if necessary

Excessive calcium, gum and other material in roller train

Apply a calcium rinse or hot water/white vinegar (2:1) rinse

Roller train and fountain solution too cold

Set rollers to 72°-80°F (22°-26°C) and water pan to 65°F (18°C)

Fountain solution too mild

Ensure chemistry has enough etch and alcohol substitute per manufacturer’s recommendations

Streaks in Print (non-gear streaks)

Blanket is over-packed causing a bump when striking the plate and jarring the form rollers. This creates a bounce and/or skid producing a streak

Tension blankets to press manufacturer’s specifications

Streaks appear across the sheet one revolution back from the top of the plate. Ink form rollers are set too heavily to the plate or durometers are too high

Check durometer of rollers and replace if necessary. Set rollers to pressures specified by the press manufacturer

Slurring

Inspect pressure between blanket and plate or between the blanket and paper

Pack to press manufacturer’s specifications

Blanket tension low

Tension current blanket (or new) to press manufacturer’s specifications

Grippers out of calibration

Check and reset all grippers to press manufacturer’s specifications

Paper with wavy edges or other distortions

Check on a different stock to see if slurring remains. If not, change stock or consult your paper supplier

Poor Scuff Resistance

Ink film not fully dry

Make sure the ink film is thoroughly dry. An oxidizing ink should take 24 to 48 hours to thoroughly dry. Many variables: substrate, fountain solution, ink coverage, ambient conditions

Ink is over-emulsified

Check pH and conductivity and Brix level of fountain solution. Run less fountain solution to achieve proper ink/water balance

Chalking – ink not binding to substrate

Certain papers can be very absorbent leaching away the ink vehicle and leaving the pigment unbound on the surface

Piling

Verify whether the pilling is defective paper coating or ink

If defective paper coating, try a different batch of paper or lower the tack of the ink slightly if necessary

If the Ink becomes over-emulsified/waterlogged, this changes the physical properties of the ink and results in poor transfer

Check that pH, conductivity, Brix level and tempera-ture are to specification and try to run less water

Ink roller train or ink fountain is too cool

Adjust form rollers to 72°-80°F (22°-26°C) and be sure ink fountain is 70°F (21°C) or above to ensure proper ink flow and transfer

Inadequate or excessive blanket cylinder pressure and/or plate or blanket packing

Check blanket cylinder pressures and/or plate and blanket packing are all to manufacturer’s specifica-tions

Rollers are the wrong durometer or improperly set

Check roller settings, clean and condition / deglaze rollers

Ink film thickness may be too high or too low

Verify densities are in normal range

Ink is poorly ground

Check grind. Consult your ink supplier

ph Conductivity Varies Widely

Water quality or supply is varying

Consider installation of a Reverse Osmosis water treatment system. Consult your fountain solution supplier

Concentration of mix is varying

Check doser for accuracy (perform a “jug test”)

Circulating system is contaminated (pressroom supplies, ink or paper)

Thoroughly rinse and clean system with warm water. Avoid contamination by using the correct application of product

Mottling

Paper has an uneven surface

Check paper for texture and absorbency. Try a different stock

Too much water is being carried; inks are water-logged

Reduce water; adjust ink/water balance, check chemistry

Too much water is present in prior unit; water is left on sheet

Reduce water from prior unit

Stock is weak or paper coating is too soft

Reduce ink tack

Excessive pressure exists between blanket, plate and/or stock

Ensure all pressures and packing are within manufacturer’s specifications

Blanket is too hard or glazed

Change to softer blanket or deglaze

Ink is too strong; insufficient ink is being carried to the plate

Weaken ink strength by adding transparent white