Troubleshooting Guide - Pressroom Conventional
On Press Issue: Back Trap Mottling
Potential Causes
Using fast setting work and turn inks
Solution: Use a more stable, slower setting ink with lower solvent content.
Dark colored inks printed on the first or second units
Solution: Change ink sequence. Run darker colors last in sequence if possible.
Solid overprinted by another solid or screen tint
Solution: Change layout and/or sequence if possible to print lighter coverage forms before heavier coverage forms.
Improper tack sequence
Solution: Use tack graded inks, printing highest tack inks first, or use properly formulated uniform tack inks.
Ink drying on rollers and blankets during long make readies
Solution: Clean press and shorten make ready times.
Excessive solvent evaporation due to fast press speeds
Solution: Reduce press speed and use fresh ink.
Running glossy substrate
Solution: High gloss substrates are prone to back trapping. Try a lower gloss substrate if possible.
Running compressible blanket
Solution: Change to a quicker release conventional blanket with high solvent resistance.
Excessive blanket squeeze
Solution: Back off pressure on back cylinder slightly.
Potential Causes
Ink film is too thin because ink strength is too strong
Solution: Reformulate ink or make weaker at press by adding extender or tint base.
Fountain solution pH too low
Solution: Check pH of solution. pH of lower than 3.5 can slow drying. Adjust pH of fountain solution.
Ink body is too soft causing excess penetration into substrate
Solution: Reformulate ink for heavier body showing penetration. Heavy body, high solid varnishes added at press will help.
Potential Causes
Gripper settings
Solution: Worse on one side of sheet. Adjust gripper settings.
Paper unstable and fanning in successive units
Solution: Try different substrate, reduce back pressure, reduce water. Paper grain may be running in the wrong direction.
Loose plate
Solution: Secure plate.
Loose blanket
Solution: Tighten blanket clamps, adjust packing, or replace blanket.
Potential Causes
Ink taking on too much water
Solution: Adjust ink/water balance.
Ink film thickness is excessive
Solution: Run less ink. Check formula for proper ink strength. Increase strength of ink if appropriate.
Solid overprinted by another solid or screen tint
Solution: Change layout and/or sequence if possible to print lighter coverage forms before heavier coverage forms.
Improper tack sequence
Solution: Use tack graded inks, printing highest tack inks first, or use properly formulated uniform tack inks.
Ink drying on rollers and blankets during long make readies
Solution: Clean press and shorten make ready times.
Excessive solvent evaporation due to fast press speeds
Solution: Reduce press speed and use fresh ink.
Running glossy substrate
Solution: High gloss substrates are prone to back trapping. Try a lower gloss substrate if possible.
Running compressible blanket
Solution: Change to a quicker release conventional blanket with high solvent resistance.
Excessive blanket squeeze
Solution: Back off pressure on back cylinder slightly.
Potential Causes
Large solids are printed on back-up form
Solution: Print the heavy form first, and the light form on the back-up side.
Problem may be caused by large lifts
Solution: Run small loads when backing up the sheets to improve exposure to air.
The first side is backed up too soon after it is run
Solution: Hold the lifts three days before printing back-up sides.
Tips to prevent or minimize ghosting
Solution:
- Wind sheets before printing back-up side
- Keep lifts in sequence for back-up.
- Keep lifts away from sources of excessive heat and cold.
- On small expensive runs, slip-sheet the stock while printing the second side.
Tips to save job that has ghosted
Solution:
- Size with dull varnish then apply gloss varnish.
- Run sheets through the press without printing to supply fresh air before back-up is printed. Heat helps.
- Wind sheets frequently and wait.
Potential Causes
Poor layout
Solution: Improve layout or tilt images on sheet a maximum of 7 degrees.
Ink film is too thin
Solution: Weaken ink so a heavier ink film may be carried.
Ink is too transparent
Solution: Make ink more opaque with opaque white or silver.
Potential Causes
Too much water reaching paper
Solution: Reduce dampener setting for proper performance.
Paper surface contains trash, coating duet, or trimmer dust
Solution: Make tape pulls from the blanket for analysis. Consult paper manufacturer.
Substrate isn't resistent to picking
Solution: If picking is serious, reject substrate and change to a more pick-resistent substrate.
Impression pressure set too high for ink/substrate combination
Solution: Reduce impression pressure, repack to manufacturer specifications.
Blanket is in poor condition
Solution: Change to a less tacky/quick release blanket. Check blanket wash, may be attacking blanket surface and making it tacky.
Potential Causes
Ink is waterlogged
Solution: Reduce dampener settings. Check for proper fountain solution, pH and conductivity.
Ink is drying too fast on rollers
Solution: Check formula for excessive dryer, reformulate if necessary. Add small amounts of antioxidant.
Ink is too strong
Solution: Review formula and proof. Reduce strength with good transfer varnish or additive.
Blankets and plates are underpacked
Solution: Check packing per press manufacturers specifications.
pH is low or conductivity is too high
Solution: Check with meter and adjust.
Fountain solution is too cold
Solution: Fountain solution should be 60 degrees F +-5. Adjust if necessary, especially if too cold.
Potential Causes
Blanket is swollen or embossed
Solution: Change blanket and use packing gauge (if possible) to check pressure.
Rollers are too hard or in poor condition
Solution: Check with durometer gauge. Replace rollers as needed.
Ink and dampening form rollers set incorrectly
Solution: Set to correct specification.
Abrasive particles are destroying image
Solution: Check ink grind, fountain solution, solvents, etc. Replace all contaminated material.
Plate is incompletely developed, leaving gum on imaged areas
Solution: Wash plate. If problem persists, have plate remade.
Plate and blanket are improperly packed
Solution: Check packing with packing gauge. Improper packing causes different surface speeds between plate and blanketand will wear image prematurely.
Ink and dampening rollers are set too hard to the plate
Solution: Stripe rollers to the plate. Review press manufacturers specifications and adjust if necessary.
Potential Causes
Plates are processed improperly
Solution: Check plate developing process, include Stouffer scale.
Ink and/or water form rollers improperly set
Solution: Adjust to manufacturer's specifications.
Excessive linting
Solution: See picking/linting.
Fountain solution is too concentrated
Solution: Check conductivity and adjust as necessary. Make fresh solution.
Plate and blanket cylinders improperly packed
Solution: Check with a Cologht or Baldwin gauge and set to manufacturer's specifications.
Plates are run beyond their capabilities
Solution: Switch to a higher quality plate which will result in longer plate life.
Inks are too strong resulting in starving the image area
Solution: Reduce strength of inks to improve plate lubrication.
Ink has extremely poor grind
Solution: Check ink grind. Regrind or re-make ink.
Form rollers are too hard
Solution: Check with durometer gauge. Replace form rollers if needed.
Potential Causes
Fountain solution has too little acid
Solution: Check conductivity vs manufacturers specifications. Adjust fountain solution mixture to manufacturers specifications.
Running too much fountain solution on dampeners
Solution: Reduce dampener settings.
Dampening rollers or blanket are gazed
Solution: Clean with chemical deglazer. Use metering roller cleaner on dampening rollers.
Ink rollers are glazed
Solution: Treat rollers with Copperizing solution. Check with manufacturer of fountain solution for proper ratio of gum in solution.
Ink is too strong
Solution: Examine formula, proof out to determine if ink is too strong. Reduce ink strength with tint base.
Tip
Solution:
- Wash rollers with white vinegar for 15 minutes. Rinse rollers with warm water for 15 minutes or perform calcium wash.
Potential Causes
Too much water being used
Solution: Reduce dampener settings.
Paper contains an excessive amount of water
Solution: Change paper.
Color contains Reflex (Alkali)
Solution: Reformulate without Reflex Blue or use imitation Reflex Blue.
pH in fountain solution is too high
Solution: Adjust pH and conductivity to proper specification.
Ink isn't completely dry
Solution: See Drying.
Roughness creates poor rub between unprinted and printed surface
Solution: Change substrate to smoother surface. Aqueous coat or varnish to protect.
Too much ink being run
Solution: Lower level of ink use.
Ink is improperly formulated for rub-resistance
Solution: Review formula.
Potential Causes
Fountain solution conductivity is out of specification
Solution: Check conductivity to manufacturers specification. As a guideline, if solution is more than 1000 over a fresh properly mixed solution, it should be replaced with fresh solution.
Glazed blanket, ink rollers, or dampening rollers
Solution: Clean thoroughly and recondition per manufacturers instructions.
Excessive printing pressure
Solution: Make on-press adjustments to proper pressures.
Ink body is too soft in body and spreading into non-printed areas
Solution: Reformulate as necessary.
Plate improperly developed
Solution: Clean with plate cleaner or remake plate.
Dampening rollers out of adjustment or worn out
Solution: Adjust rollers or replace as needed.
Overheated ink rolls
Solution: Check for worn bearings, adjust roller pressure if necessary.
Potential Causes
Ink setting too slow
Solution: Change to faster setting ink.
Excessive amount of water being run
Solution: Check pH and conductivity of fountain solution. Run as little ink and water as possible, especially on non-porous substrates.
Insufficient spray powder used or not distributed evenly
Solution: Increase powder application. Visually check for the amount and the evenness of distribution with a blacklight.
Loads too high for stock weight
Solution: Run shorter lifts, tray the lifts, wind sheets.
Static electricity
Solution: Use static eliminators.
Pile temperature too hot
Solution: If temperature is over 100 degrees F, the ink could resoften and block or set off. Reduce heat in delivery dryers. Winding sheets could dissipate heat quicker.
Spray units clogged
Solution: Visually examine spray units and clean/unclog if necessary.
Improper particle size of spray powder being used
Solution: Check on spray powder container for particle size. Check with manufacturer for proper particle size for the weight of substrate being used. The heavier the substrate, the larger of particle size is required.
Potential Causes
Too much ink on rollers
Solution: Reduce amount of ink carried, increase ink strength to allow carrying less ink on rollers.
Ink/water balance incorrect
Solution: Adjust ink/water balance. Try reducing ink and water.
Ink body too long
Solution: Make shorter body.
Rollers set incorrectly
Solution: Reset rollers to specification.
Rollers in poor condition
Solution: Replace rollers as needed.
Excessive heat on press
Solution: Heat messures on press rollers over 90 degrees F could cause misting.
Potential Causes
Too much ink on rollers
Solution: Adjust packing to equalize diameters of cylinders. If diameters differ, the resulting different speeds between cylinders causes slippage resulting in a slurred image.
Loose, uneven, or soft blanket
Solution: Tighten blanket clamps, adjust packing, or replace blanket.
Excessive play in gears and bearings of plate and blanket cylinders
Solution: Adjust to manufacturers specifications.
Running too much ink on coated substrate
Solution: Reduce the amount of ink carried. Increase ink strength to allow carrying less ink on rollers.
Potential Causes
Fountain solution concentration incorrect
Solution: Adjust pH and conductivity to proper specification.
Ink/water balance incorrect
Solution: Adjust to proper ink/water balance.
Too much pressure between plate and blanket
Solution: Set to manufacturers specifications.
Setting/durometer of dampener and ink rollers out of specification
Solution: Set rollers to manufacturers specifications. Replace rollers if durometer is not correct.
Ink not water resistant
Solution: Review formula. Add water resistant additive if necessary.
Plate improperly exposed or developed
Solution: Correct plate making procedure.
Fountain solution contaminated
Solution: Change fountain solution.
Paper coating contaminating the ink train
Solution: Use low tack inks, low water settings and low pressure settings consistent with good reproduction.
Potential Causes
Ink and dampening settings may be out of specification
Solution: Set ink and dampening balance correctly, and check continuously throughout run.
Too much water in ink train
Solution: Wash rollers, lower water settings.
pH setting too low
Solution: Adjust pH level in fountain solution to ideal setting (no lower than 4.5).
Very little image in printed area
Solution: Where there is less ink taking, an additional ink stripe may be introduced to stabilize the balance of ink and water.
Form/dampening roller settings out of specification
Solution: Inspect and adjust inking dampening rollers if necessary.
