Glossary

Screen printing terms, in plain words

The shorthand our guides use, defined once. Guide pages link the first use of each term back here.

AATCC: American Association of Textile Chemists and Colorists. It publishes standard textile tests, including the gray scales used to rate color change and staining.
Capillary film: A pre-made emulsion film you apply to wet mesh instead of coating liquid emulsion. It gives an even, repeatable EOM.
Choke: Shrinking an underbase slightly so it hides under the top colors and doesn’t peek out at the edges.
Diazo emulsion: An emulsion you sensitize (mix) before use. Low cost and forgiving, with wide exposure latitude, but slower to expose; about 3 months’ life once mixed.
Discharge ink: A water-based ink with an activator that removes the shirt’s dye and replaces it with pigment. Works on dyed natural fibers, not on polyester.
Dmax: The darkest density a film positive reaches. Higher Dmax blocks more UV light, so the image washes out cleanly.
Dual-cure emulsion: An emulsion that combines diazo and photopolymer: wide latitude with good detail. It must be mixed before use.
Durometer: How hard a squeegee blade is, on the Shore A scale. 60A is soft, 70A is the all-round middle, 80A is hard.
Dwell: Time the print spends inside the heated part of a conveyor dryer.
Dye migration: Shirt dye, often in polyester, moving into the ink when heated, so white turns pink or gray.
EOM: Emulsion over mesh: how far the emulsion stands above the mesh on the print side. More EOM gives a thicker ink deposit.
Exposure calculator: A test film with several filters that each let through a different share of light. One long exposure shows which step looks best, and each step has a factor you multiply your test time by.
Fibrillation: Tiny shirt fibers poking up through the ink so the print looks fuzzy or dull, often worse after the first wash.
Flash (flash cure): Briefly heating a print until it’s dry to the touch, so the next color can print on top. It is not a full cure.
Flood stroke: A light pass that fills the screen’s open areas with ink without printing, so the print stroke lays down an even layer.
Gel (gel point): When plastisol firms up and feels dry to the touch. A gelled print is not cured: the whole ink film still has to reach its cure temperature.
Halftone: A pattern of dots of different sizes that prints shades and gradients with one solid ink.
Low-bleed ink and blocker: Inks made to resist dye migration on polyester. A blocker is a gray or black base layer printed underneath to stop the dye reaching the top colors.
LPI: Lines per inch: the line count of a halftone. A higher LPI gives smaller, finer dots and needs a finer mesh.
Mesh count: Threads per inch in the screen fabric. Lower counts pass more ink; higher counts hold finer detail.
Micro-registration: Fine-adjustment knobs on a press head that move a screen a little at a time to line up colors.
Moiré: A wavy, plaid or checkerboard pattern that appears when the halftone dot grid clashes with the mesh, the knit or patterns in the art.
N/cm: Newtons per centimeter, the unit a tension meter reads. Higher numbers mean a tighter screen.
NEMA 5-15P and 5-20P: Standard US plug types. A 5-15P is the ordinary 15-amp plug. A 5-20P has one sideways blade and needs a 20-amp outlet.
Off-contact: The gap between the screen and the shirt when the screen is at rest. The screen should touch the shirt only under the squeegee.
Plastisol: The most common T-shirt ink. It doesn’t air-dry in the screen; it cures with heat.
Platen (pallet): The flat board the shirt sits on while you print. Also called a pallet; our guides say platen. “Pallet adhesive” and “platen adhesive” are the same thing.
Print side and squeegee side: The two sides of a screen. The print side (also called the shirt side) faces the shirt; the squeegee side faces you and holds the ink. Coating from the squeegee side pushes emulsion through to the print side.
Reducer: An additive that thins ink. Use a curable reducer at the dose the ink maker allows: too much, or a non-curable one, can stop plastisol from curing.
Registration: Lining up each screen so every color lands where it should.
RIP: Raster image processor: software that turns art into film or screen output and controls the halftone dots, line count and angle. AccuRIP is one example.
SBQ: A pure photopolymer emulsion chemistry. SBQ emulsions come pre-sensitized and expose quickly.
SDS: Safety data sheet: a product’s chemical safety sheet, covering hazards, handling and protective gear.
Simulated process: A separation style for dark shirts that uses spot inks and halftones to imitate full-color art.
Spot color: Each color printed as its own solid ink from its own screen.
Step wedge (21-step): A test strip of 21 gray steps, each blocking a little more light. After exposure and washout, the step you reach shows whether the screen got more or less light than you were aiming for.
TDS: Technical data sheet: the ink maker’s spec sheet. It lists the cure temperature and time and other settings for that ink. When a guide and the TDS disagree, follow the TDS.
Trap: A slight overlap between neighboring colors so small registration shifts don’t leave gaps.
UCC-1: A public financing statement a lender files to claim an interest in equipment. Before buying used gear, make sure any UCC-1 is cleared.
Underbase: A first layer, usually white, printed and flashed under the colors on dark shirts.
Zero point: The lightest squeegee pressure that clears the ink in one stroke.