Glossary

GLOSSARY

Amphoteric
This property indicates that a molecule has both cationic and anionic sites available. A higher net negative charge reduces the potential for protein shock and results in lower viscosity.

Binder Migration Control
The ability to minimize the redistribution of the binders during drying, and to control the movement of the binders towards the coating surface or the coating/fiber interface.

Blade Scratches
This term refers to defects found on a coated sheet in the form of actual scratches or streaks. Scratches can result from a variety of reasons, including: pigments; contaminants or grit in raw materials; fibers picked off the surface; poor screening; poor rheology of coating; wet end problems, such as slime or poor quality pulp; contaminants from the size press; and improper water holding of a coating. (Blade scratching can result from not only the coating, but from the base sheet itself.)

Coating Porosity
The amount of continuous void volume in a dried coating. Porosity is important for blister resistance in offset printing. Porosity also affects fountain solution acceptance, ink receptivity, and ink holdout.

Coating Rheology
The flow or response of the coating under shear (or mechanical action).

Coating Structure
The physical distribution or arrangement of the coating components in the dried state. Generally, when speaking of increased structure, increased void volume is implied.

Dilatant
The rheological property of a coating in which viscosity increases with increasing amounts of shear (shear thickening).

Fiber Coverage
The ability of the coating to fill the spaces between the fibers of a sheet to create a smooth uniform surface with minimum coatweight for quality printing.

Glueability
The ability of coated boxboard to accept adhesive and form strong bonds. Also, glueability refers to the speed at which the bonding is achieved.

Hold-out
The degree to which a sheet resists penetration. This term can be further classified as:

Coating Holdout

– the degree to which a coating remains on the surface of a sheet.

Ink Holdout

– the degree to which a coating holds ink on the surface.

Hydrophilic
This term refers to a particle or substance having a strong affinity for water.

Immobilization Solids
This expression refers to the solids level at which a redistribution of the coating components no longer occurs during drying. This is the point where binder migration ceases.

Viscosity Immobilization Solids

-- that solids level at which a redistribution of the coating components no longer occurs during drying, or the point at which binder migration ceases (measured under low shear conditions).

Running Immobilization Solids

-- that solids level at which the coating becomes dilatent under the metering device (measured under high shear conditions).

Plate Immobilization Solids

-- a laboratory measure of the water loss to immobilization and the relative structuring potential in comparing formulations by measuring solids level of the coating at the point when the surface gloss is lost.

Ink Trap
The ability of ink to transfer uniformly from the offset blanket onto a previously printed area of a multicolored printed sheet.

K & N
This is a test method used to indicate coating surface uniformity as to degree of ink receptivity.

Lubricity
A property of a coating in which individual pigment particles flow amongst themselves with minimum friction. Coating lubricity or degree of abrasion can affect blade wear. Poor lubricity can cause blade streaks.

Newtonian
A rheological characteristic in which viscosity decreases proportionally to shear.

Non-Thermoplastic
The ability of a binder system to resist flow when heat and pressure are applied. Non-thermoplasticity does not allow heat softening. Sticking will be minimized during calendering, and blocking will be reduced at the dye cutter or the rewinder.

Optics
Visual properties that affect sheet appearance such as brightness, opacity, and gloss.

Porosity
An indication of the size, shape and distribution orientation of the pores in a coating and the degree to which the pores are inter-connected; involved in fluid permeability (absorption properties).

Printability
The overall characteristics of a coated surface to accept ink in a manner that is adequate for the particular printing process being employed is referred to as printability.

Print Gloss
This property refers to the ink gloss achieved with controlled ink application.

Print Mottle
The uneven acceptance of ink onto the coated surface. There are basically two print mottles that occur in the offset printing process:

Back Trap

– this occurs when ink from a previous station transfers onto a subsequent station. When this occurs, one impression follows another too rapidly (ink vehicle has been held out too much causing the ink to remain fluid).

Wet Trap

(water interference or ink refusal) – this occurs when fountain solution is unevenly or inadequately absorbed into the sheet. If the fountain solution has not absorbed fast enough, the surface remains damp and will not receive ink uniformly.

Pseudoplastic Flow
A rheological characteristic in which weak internal structuring within the coating itself causes the coating to resist flow until enough shear is applied to overcome this structuring, i.e., viscosity is inversely proportional to shear; as shear increases, viscosity decreases.

Rheology
The flow properties of a coating system.

Runnability
The coating’s ability to respond appropriately to the metering methods employed during the actual coating process.

Thixotropic
The viscosity of a coating in response to shear – the viscosity of the coating will be lower after being sheared than prior to being sheared. Most coatings are pseudoplastic/thixotropic and are incorrectly called thixotropic.

Uniform Ink Receptivity
Surface characteristics that result in mottle free printing.

Viscometer
An instrument used to measure a coating’s flow characteristics under shear.

Hercules Viscosity

– a high shear viscosity measurement that is helpful in predetermining how a coating will meter-off under operating conditions.

Brookfield Viscosity

– a low shear viscosity measurement that is helpful in predetermining how a coating will pump and flow through a coating system.

Void Volume
The fraction of the total coating volume that is open space between components in a coating; involved in light scattering (optical properties).

Water Retention
The ability of a coating to hold water, controlling penetration into the substrate and evaporation at the coating surface.

Wet Rub
A coating’s resistence to wet abrasion as takes place in non-printed areas on an offset press.

Zeta Potential
This is a measurement of the electrostatic repulsive force between two charged particles. Zeta potential measures flocculation potential of a coating.


			GLOSSARY Amphoteric This property indicates that a molecule has both cationic and anionic sites available. A higher net negative charge reduces the potential for protein shock and results in lower viscosity. Binder Migration Control The ability to minimize the redistribution of the binders during drying, and to control the movement of the binders towards the coating surface or the coating/fiber interface. Blade Scratches This term refers to defects found on a coated sheet in the form of actual scratches or streaks. Scratches can result from a variety of reasons, including: pigments; contaminants or grit in raw materials; fibers picked off the surface; poor screening; poor rheology of coating; wet end problems, such as slime or poor quality pulp; contaminants from the size press; and improper water holding of a coating. (Blade scratching can result from not only the coating, but from the base sheet itself.) Coating Porosity The amount of continuous void volume in a dried coating. Porosity is important for blister resistance in offset printing. Porosity also affects fountain solution acceptance, ink receptivity, and ink holdout. Coating Rheology The flow or response of the coating under shear (or mechanical action). Coating Structure The physical distribution or arrangement of the coating components in the dried state. Generally, when speaking of increased structure, increased void volume is implied. Dilatant The rheological property of a coating in which viscosity increases with increasing amounts of shear (shear thickening). Fiber Coverage The ability of the coating to fill the spaces between the fibers of a sheet to create a smooth uniform surface with minimum coatweight for quality printing. Glueability The ability of coated boxboard to accept adhesive and form strong bonds. Also, glueability refers to the speed at which the bonding is achieved. Hold-out The degree to which a sheet resists penetration. This term can be further classified as: *Coating Holdout* – the degree to which a coating remains on the surface of a sheet. *Ink Holdout* – the degree to which a coating holds ink on the surface. Hydrophilic This term refers to a particle or substance having a strong affinity for water. Immobilization Solids This expression refers to the solids level at which a redistribution of the coating components no longer occurs during drying. This is the point where binder migration ceases. *Viscosity Immobilization Solids* -- that solids level at which a redistribution of the coating components no longer occurs during drying, or the point at which binder migration ceases (measured under low shear conditions). *Running Immobilization Solids* -- that solids level at which the coating becomes dilatent under the metering device (measured under high shear conditions). *Plate Immobilization Solids* -- a laboratory measure of the water loss to immobilization and the relative structuring potential in comparing formulations by measuring solids level of the coating at the point when the surface gloss is lost. Ink Trap The ability of ink to transfer uniformly from the offset blanket onto a previously printed area of a multicolored printed sheet. K & N This is a test method used to indicate coating surface uniformity as to degree of ink receptivity. Lubricity A property of a coating in which individual pigment particles flow amongst themselves with minimum friction. Coating lubricity or degree of abrasion can affect blade wear. Poor lubricity can cause blade streaks. Newtonian A rheological characteristic in which viscosity decreases proportionally to shear. Non-Thermoplastic The ability of a binder system to resist flow when heat and pressure are applied. Non-thermoplasticity does not allow heat softening. Sticking will be minimized during calendering, and blocking will be reduced at the dye cutter or the rewinder. Optics Visual properties that affect sheet appearance such as brightness, opacity, and gloss. Porosity An indication of the size, shape and distribution orientation of the pores in a coating and the degree to which the pores are inter-connected; involved in fluid permeability (absorption properties). Printability The overall characteristics of a coated surface to accept ink in a manner that is adequate for the particular printing process being employed is referred to as printability. Print Gloss This property refers to the ink gloss achieved with controlled ink application. Print Mottle The uneven acceptance of ink onto the coated surface. There are basically two print mottles that occur in the offset printing process: *Back Trap* – this occurs when ink from a previous station transfers onto a subsequent station. When this occurs, one impression follows another too rapidly (ink vehicle has been held out too much causing the ink to remain fluid). *Wet Trap* (water interference or ink refusal) – this occurs when fountain solution is unevenly or inadequately absorbed into the sheet. If the fountain solution has not absorbed fast enough, the surface remains damp and will not receive ink uniformly. Pseudoplastic Flow A rheological characteristic in which weak internal structuring within the coating itself causes the coating to resist flow until enough shear is applied to overcome this structuring, i.e., viscosity is inversely proportional to shear; as shear increases, viscosity decreases. Rheology The flow properties of a coating system. Runnability The coating’s ability to respond appropriately to the metering methods employed during the actual coating process. Thixotropic The viscosity of a coating in response to shear – the viscosity of the coating will be lower after being sheared than prior to being sheared. Most coatings are pseudoplastic/thixotropic and are incorrectly called thixotropic. Uniform Ink Receptivity Surface characteristics that result in mottle free printing. Viscometer An instrument used to measure a coating’s flow characteristics under shear. *Hercules Viscosity* – a high shear viscosity measurement that is helpful in predetermining how a coating will meter-off under operating conditions. *Brookfield Viscosity* – a low shear viscosity measurement that is helpful in predetermining how a coating will pump and flow through a coating system. Void Volume The fraction of the total coating volume that is open space between components in a coating; involved in light scattering (optical properties). Water Retention The ability of a coating to hold water, controlling penetration into the substrate and evaporation at the coating surface. Wet Rub A coating’s resistence to wet abrasion as takes place in non-printed areas on an offset press. Zeta Potential This is a measurement of the electrostatic repulsive force between two charged particles. Zeta potential measures flocculation potential of a coating.