Glossary of Common Screen Printing Terms
ADHESION TEST: any of a
diversity of test methods used to
determine
the adequacy of ink or coating adhesion to a
substrate.
A commonly used test method is ASTM#D-3359,
also
referred to as the Cross-cut tape test.
BINDER; the segment of the vehicle
in an ink composition
that,
in combination with the pigments, forms a film.
BLEED: I. the spreading or
migration of an ink component
or
dye into an area where it is not wanted; 2. the spreading or
running
of a pigment color by action of a solvent.
BLOCKING: an undesired adhesion
between layers of
material
placed in contact under moderate pressure and/or
temperature
in storage or use. Usually occurs in a stacked
prior
to thorough drying.
BLOOM; the bluish-gray milky veil
which appears on the
surface
of prints under adhesive conditions of heat and
humidity.
It is usually the result of too rapid solvent
evaporation
which causes condensation of moisture on the
surface.
CATALYST: a substance which has
the capability of
initiating
or accelerating the speed of a reaction between two
or
more substances when introduced into their presence,
normally
in relatively small quantities.
CHALKING: a condition of a screen
printed ink in which
the
pigment is not properly bound to the substrate and can
be
easily rubbed off, usually after exposure to the elements.
Typically
degrades to a dry powder.
CHEESEY: a term used in evaluating
the degree of curing in
a
plastisol ink film, usually describing and undercured state.
CHEMICAL RESISTANCE: the
resistance of an ink film
or
imprint to deteriorating effects resulting from exposure to
or
immersion in chemicals of specified type under specified
conditions.
CLOGGING: premature drying of ink in
the printing
screen
which causes imperfect prints by blocking portions of
the
open stencil.
COBWEBBING: fine filaments produced by
the ink
between
the screen fabric and the substrate, resulting in a
cobweb-like
appearance on the finished print. It may be
reduced
to a minimum by careful selection of solvents and
proper
adjustment of printing conditions.
COMBUSTIBLE LIQUID: a liquid
having a flash point at
or
above 100 degrees F. (37.8 degrees C.) but less than 200
degrees
F. (93.3 degrees C.).
CORONA DISCHARGE: an
electrical, surface treating
method
whereby the atmosphere (corona) around the
substrate
is ionized, encouraging oxidation and reducing
surface
tension for improved ink adhesion.
CRATERING: small undesirable
depressions in a dried ink
film
which may be so deep as to expose the substrate.
CRAWLING: the contraction of an ink
into drops after
printing
onto a surface which the ink does not wet com-
pletely.
CRAZING: I. a cracking and/or removal
of ink from areas
of a
posted printed poster; 2. a random pattern of minute
intersecting
cracks in plastic, ceramic glaze, or other surfaces.
CROCKING: printed image rub-ofF(wet or
dry) of surface
color
that can occur when a dye or pigment is not adequately
fixed
in the substrate.
DEGREASING; the removal of dirt and oils
from the
stretched
screen fabric before coating or applications of
stencils. May include roughening of the fabric surface
or
application
of adhesion-promoting chemicals.
DENSITOMETER: a photoelectric device that
measures
either
the reflected or transmitted density of photographic
film
or printed color.
DIAZO: a photosensitive chemical
which sensitizes photo-
screen
making emulsions to actinic light.
DIRECT EMULSION: a liquid
photo-polymer emulsion
used
as a screen printing stencil which is coated onto a
stretched
screen, dried, exposed through an imaged film
positive
by actinic light and developed.
DIRECT/INDIRECT PHOTOSCREEN STENCIL:
a
stencil
made by adhering a gelatin coated sheet to the
underside
of the tensioned screen fabric with a photosensi-
tized
emulsion, drying, exposing through a film positive to
actinic
light, developing and stripping away of the gelatin's
plastic
support sheet.
DOT GAIN: the tendency of
the printed halftone dot to
change
in size at the moment of ink imprinting, thus
changing
the overall visual quality of the print. Due to a
number
of variables, the printed dot will be larger than its
film
counterpart. Also called Dot Growth or Dot Spread.
DRAIZE TEST: a method for
estimating the skin or eye
irritation
due to contact with a chemical substance.
DRAWDOWN: a film of ink deposited
uniformly on a
substrate
by means of a smooth edged blade or cylindrical
rod,
to evaluate the undertone, mass tone, etc., of an ink.
DRYING: a multistage process
describing the solvent
evaporation
and/or film formation of screen printing inks and
coatings
(not to include curing, a separate process). Various
stages
include set-to-touch; dust-free; tack-free; dry-to-touch;
dry-hard;
dry-through; and dry-to-recoat.
EDGE CURL: the tendency of
a pressure sensitive sheet to
deform
or bend away from the surface to which it has been
adhered.
EVAPORATION RATE: the speed at
which a solvent, or
any
liquid evaporates.
EXEMPT
SOLVENTS: descriptive of evaporative solvents
not
currently subject to air pollution regulation.
EXTENDER BASE (EXTENDER): a
non-pigmented
compound
used in screen printing to increase ink volume
without
reducing viscosity. Ordinarily, it is a buttery semi-
paste
that has no effect on ink color except to reduce its
intensity
of hue.
FADING: partial or complete loss of
color due to excess
heating
or environmental influences; a gradual "bleaching
out"
appearance of a color from a print, common causes:
(a)
intense sun exposure; (b) too much "watering down" of
ink
with solvents during printing; (c) lack of wash resistance
of
garment inks or dyes.
FINENESS
OF GRIND: the degree of dispersion of
pigment
particles in a vehicle.
FISH EYE: a flaw in a
screen printed ink film consisting of a
circular
defect caused by the slight bubbling of the ink with
resulting
dispersion of the pigment within the immediate area,
causing
a non-uniformity of color in what appears to be a hole
or a
void.
FLAGGING: corners of sheets of an
outdoor poster releasing
from
the background due to improper paste or posting, or to
having
ink on the back of sheets.
FLAME TREATED PRODUCT;
a container or other
object
typically formed ofpolyethylene or polypropylene
plastic,
the surface of which has been oxidized by contact with
a
flame to disperse surface solvents to prepare the object for
printing.
FLAMMABLE
LIQUID: a liquid having a flash point below
100°
F. (37.8° C.) with the exception of any liquid mixtures
which
have one or more components with a flash point at or
above
100° F. in a concentration of 99% or more of the total
volume
of the mixture.
FLASH CURE; a stage in the
e plastisol curing process
generally
used between ink laydowns. Usually modular units
are
employed to accomplish this step, which are not designed
to
completely cure the plastisol film. Also referred to as Spot
Cure.
FLASH POINT: the minimum
temperature of a saturated
vapor
of a specified liquid, at which the vapor will ignite in the
presence
of a spark or flame, under specified conditions.
FLATTING AGENT: any material added to
reduce the gloss
level
of an ink or coating,
FLOCCULATION; the process by which an
aggregation of
pigment
particles in ink, caused by a flocculant, form clusters
or
chains; usually accompanied by a change in the chroma
and/or
hue of the color of the ink. Also called Livering.
FLOW AGENT: an additive
used to disturb the surface
tension
and increase the ink flow, when bubbles or orange-
peel
occur.
FOUR COLOR PROCESS PRINTING:
a method of
reproducing
full-color artwork by photographically separating
the
art into its three subtractive primary colors; yellow,
magenta
and cyan, plus black and then printed through a set
of
color-separated halftone printing screens.
FOUR COLOR SEPARATIONS:
the term applied to films,
either
negative or positive, totaling four in number, each
having
the total image elements for one of the four colors used
in
four color process printing. The separations may be made
by
use of a process camera or more sophisticated electronic
scanner
devices.
GEL: a state or condition in
which an ink or vehicle
demonstrates
a semi-solid or jelly-like consistency. Can refer
to
the deterioration of a material to an unworkable substance.
HALFTONE: an image in which details
and dark and light
tones
are represented by dots of varying sized in relationship to
the
tones and shades which they must reproduce. Small dots
form
light tones and larger dots form darker tones.
HEAT
SEALING:
uniting two distinct surfaces by fusion,
either
of the coatings or of the base materials, under
controlled
conditions of temperature, pressure, and time
(dwell).
HEAT TRANSFER APPLICATION:
the process of image
transfer
to substrate by application of heat.
HEAVY METALS: generally
toxic metallic elements
contained
in some pigments, e.g., chromium, cadmium,
lead,
etc.
HIDING POWERS: the ability
of a paint, ink or coating
material
used to hide or obscure a surface to which it has
been
uniformly applied, under specified conditions.
HYDROPHOBIC: lacking affinity for water;
the opposite
ofhydrophilic.
HYGROSCOPIC: the quality of some
materials to absorb
atmospheric
moisture; exhibiting an affinity for water.
JET DRYING:
the drying of screen printed material by
means
of a jet dryer.
LEAD-FREE INK: inks formulated
with the absence of
lead
and used for special purposes where the presence of lead
would
constitute a danger. In the U.S., "lead-free" coatings
must
contain less than 0.06% lead by weight to meet certain
regulations.
LEAFING: a phenomenon by which
metallic pigments
form
a layer parallel to the surface of the substrate, thereby
yielding
a high metallic luster.
MAR RESISTANCE: property
of an ink film or varnish
which
remains unimpaired by slight abrasion, impact or
pressure.
Also called Rub Fastness or Abrasion Resistance.
MATTE
FINISH: a low-gloss or no-gloss finish.
MERCURY VAPOR LAMP: a
type of illuminant high in
actinic
value; used in camera lighting systems and in UV
curing
reactors.
MESH COUNT: the number of
openings per linear unit of
measurement,
either per inch or per centimeter, of a screen
printing
fabric.
MESH MARKS: a fine,
cross-hatch pattern left by the
mesh
of the screen printing fabric.
MESH OPENING: a measure of
the distance across the
space
between two parallel threads, expressed in microns.
MOIRE: an undesirable optical
pattern which occurs in
halftone
printing due primarily to incorrect screen angles of
the
halftone screens.
MOTTLE
(INK MOTTLE):
the spotty or uneven
appearance
of printing, which becomes most pronounced in
solid
areas.
NEWTON
VALUE; unit
of measure, used in screen fabric
tensioning,
generally expressed in Newtons per centimeter.
OFF-CONTACT: the preset distance between
the screen
and
the substrate that is to be printed.
OPACITY: the degree to which a sheet,
coating or film
obscures
a pattern beneath it or obstructs the passage of light
and
prevents one from seeing through it.
OXIDATION: the effect produced by
contact with oxygen,
either
in the atmosphere or introduced in more concentrated
form,
which produces drying in some screen printing inks.
PEARLESCENCE: a "pearl-like"
appearance produced by
adding
powdered titanium dioxide and mica pigments to
various
inks. As a general rule, the smaller the particle size,
the
more opaque the coating and the larger the particle size,
the
higher the lustre of the "pearl-like" finish of the ink.
PERCENT OPEN AREA: the
relationships between that
part
of a screen fabric that is blocked by threads (or wires)
and
that part that is open, or between threads.
PERMANENT
INKS: inks which resist fading or change of
color
when exposed to the environment.
PHOTO INITIATOR: a
substance which absorbs light and
is
directly involved in the production of initiator radicals for
polymerization
(as in UV curing).
PHOTOPOLYMER: a type of polymer that
undergoes a
distinct
change, such as deploymerizarion, on exposure to
light.
When used as a photo stencil material, it requires no
addition
of a photo sensitizer.
PIGMENT: substances that impart
color, including black
and
white.
PINHOLES; imperfections in the form of
tiny transparent
dots
that appear in printing screens or in process films after
development.
PLAIN
WEAVE: a pattern of weave whereby fabric threads
are
woven over one and under one, as opposed to twill weave
whereby
threads are woven over one, under two,
PLASTICIZERS; additives which may be added
to plastic
or
other formulations such as screen printing inks to improve
compatibility
of components and/or to improve flexibility,
workability
or distensibility of the dried product.
PLASTISOL FUSION RATES:
the fusing required by a
plastisol
deposit with the application of a specific temperature
elevation.
POST CURE: 1. the
continuation of a polymerization
(curing)
process within a UV ink or coating after exposure to
UV
radiation has been terminated; 2. a final or more
complete
resolving of organic materials after the initial curing
process.
POST HARDENING: the
process of further hardening a
photo
emulsion stencil by subjecting the screen to additional
light
after initial exposure and image development (washout)
has
taken place.
POT LIFE: a term
indicating the length of time during
storage
in a specific container under normal storage
conditions,
that chemical composition will not lose usefulness
through
deterioration in the original container.
PUFF INK: an ink that when
heated to a specific tempera-
ture
for a definite period of time, achieves a characteristic of
three-dimensionality
by expansion.
PYROMETER: a meter for registering
heat, and which may
be
calibrated in either Fahrenheit or Celsius scales.
RADIATION: with regard to screen
printing, the term is
generally
limited to ultraviolet or infrared wavelengths of light
and
heat energy used for curing ink films, or exposing
photostencils.
RADIOMETER: an instrument, usually self
contained, for
measuring
UV energy inside of curing units.
RECLAIMING: the process of removing both
ink and
stencil
from the screen fabric after a printing run in order to
reuse
the fabric.
REDUCER: a solvent or other additive
used for reducing
the
viscosity of an ink formulation.
RESIN: a solid or semi-solid
material of vegetable origin or
obtained
synthetically by solvent extraction, which can be
dissolved
to a liquid state, suspended in a vehicle to make an
ink
or coating, and which, upon drying, forms the solid part
of
the dried, printed film.
RETARDER; an additive for screen
printing ink that slows
down
the drying time. It is usually composed of solvents that
have
a slower evaporation rate than the solvent intended as a
dilutent
for the specific ink system.
ROLL-TO-ROLL: see Web Fed.
SAWTOOTH; the effect of stencil
material which tends to
conform
to the meshes of a screen printing fabric rather than
the
cleaner contours of the design on the film positive from
which
the stencil is produced. Both insufficient bridging and
filling-in
of the meshes produce a notched effect where lines
of
the design cross the fabric mesh diagonally.
SCOOP COASTER: a tool for
coating screen printing
fabrics
with photosensitive emulsions for making printing
screens.
Also called "Emulsion Coater:.
SCORING: I. the marking of substrate
stock with a dull
edge
to break the grain in order to facilitate creasing or
folding
along a predetermined line; 2. the slitting of the liner
paper
at intervals to permit easier release of the pressure
sensitive
film.
SCREENABILITY: a characteristic describing
how difficult
or
easy it is to print a material such as an ink, paste or coating
through
the screen.
SEEDINESS: a defect in a varnish caused
by small particles
which
sometimes become visible when examined by
transmitted
light. Varnished surfaces may present a specky or
sandy
appearance due to this defect.
SELF-TENSIONING FRAME: a screen
printing frame or
chase
with a built-in means of tensioning applied fabrics,
usually
via a screw arrangement acting upon an inner frame
or a
roller system, to which the fabric is attached.
SENSinZER: a photosensitive chemical
used for sensitizing
photographic
screen printing stencil films or emulsions.
SLIT; I. a cut through the backing
sheet or release liner of a
decal
to facilitate removal of the decal for application to the
substrate;
2. a cut through any sheet material for any purpose,
but
usually to indicate a separation line or to permit the
escape
of air if the sheet is closely contacted with another true
surface.
SOLID WASTE: a garbage, refuse,
sludge and other
discarded
material, including solid, liquid, semi-solid or
contained
gaseous material, resulting from industrial and
commercial
operations, and from community material.
SOLUTION: a uniform liquid mixture
which consists of a
solvent
or liquid and a solute, or that part which dissolves in
the
solvent.
SOLVENT: any dissolving, thinning or
reducing agent. A
liquid
that dissolves another substance, such as a resin, or used
as
an additive to reduce the viscosity or an ink.
SOLVENT-EVAPORATING INKS: inks which are
generally
dried after printing by allowing petroleum-based
solvents
to vaporize either in ambient or elevated temperature
conditions.
STATIC ELECTRICITY: a
built-up electrical charge on the
surface
of a substrate, or other surfaces, usually induced by
friction,
and most evident under low atmospheric humidity
conditions.
STREAKS: elongated defects: I. on
film, by scratching or by
uneven
application of processing chemicals, or by uneven
drying;
2. in stencils, by uneven washing out or processing or
exposure
variance; 3. on prints, by uneven squeegee edge, by a
fragment
of foreign matter in the ink, overthinning of the ink,
partial
drying in the screen of the ink, or any other condition
preventing
a uniform flow of the ink through the stencil to the
substrate.
SUBLIMATION: the process whereby certain
dyes change
directly
from a solid to a vapor and back again to a solid by
the
application of heat.
SURFACE
TENSION: the property, due to molecular
forces,
by which all liquids through contraction of the surface
tend
to bring the contained volume into a form having the
least
area. If an ink is to be compatible
with a substrate, the
surface
tension of the ink must approximate that of the surface
of
the substrate. It is measured in dynes per centimeter.
TACK: the property of a surface
which, when pressed
together
or to another surface, has a tendency to stick. The
area
of contact between two surfaces adhering together
depends
on distortion and flow within the materials.
THERMOSETTING INK: inks which
polymerize to a
permanently
solid and infusible state upon application of heat.
THINNER: a liquid which can extend a
solution but which
does
not materially impair the power of the solvent.
THKOTROPY: the property of a compound
to liquefy
under
vibrating or shearing action as by a squeegee in a screen.
This
reduction in viscosity is due to a temporary break down
of
an internal structure and dependent upon the shear history
or
the amount of previous shearing to which the material has
been
subjected.
TRAPPING OF INKS: the
property of a printing ink that
makes
it possible to superimpose one color on another, both
in
wet and dry printing.
ULTRAVIOLET STABILIZER: a
chemical compound
which
when mixed with a thermoplastic resin, selectively
absorbs
ultraviolet rays.
VACUUM
FORMING: a technique for shaping flat plastic
sheets
into contours for 3-D effects by heating the sheet until
flexible
over a mold with the desire shape or contour, then
withdrawing
the air from between the heated plastic sheet and
the
mold or die.
VEHICLE: the liquid portion of a
pigmented coating or
printing
ink including the binders or adhesives and modifiers.
VISCOMETER; an instrurnent for measuring
the viscosity
of
liquids at specified temperature and atmospheric
conditions,
by measuring the force required to move one
layer
over another without turbulence.
VOLATILE: subject to evaporation at a
relatively low
temperature.
VOLATILE ORGANIC SOLVENTS:
liquid solvents that
tend
to vaporize at room temperature, high concentrations
of
which can be injurious to ones health.
WASH RESISTANCE: the
degree of resistance of printed
textile
inks to washing in detergent solutions, without
effecting
their color strength and adhesion.
WATER BASED INKS:
inks containing a vehicle whose
binder
is water soluble or water dispersible.
WEATHERABILITY: the inherent resistance of a
product
to
weather influences when subjected to exterior exposure
conditions.
WEATHERING: the effect of atmospheric
elements on a
test
subject, when exposed out of doors in a natural
environment
or under laboratory conditions.
WEATHEROMETER: a device for testing, under
accelerated
similes of weather conditions, the resistance of a
product
to environmental influences.
WEB FED: I. an automatic
feeding system that feeds
substrates
from a continuous roll, synchronized to a stop
motion
arrangement which stops movement for printing; 2.
a
term to indicate a type of screen printing press that feeds
the
substrate from a bulk roll or bolt (as in textiles).
"WELL SIDE" OF THE
SCREEN; the upper side of a
printing
screen where the ink is placed for printing; the side opposite the side which
contacts the substrate.
WET FILM THICKNESS:
the depth, usually expressed in mils or microns, of an applied coating measured
immediately after application.
WET-ON-WET: describes the printing of
multiple colors onto a substrate before the previously printed colors have
dried.