Odisha CHSE +2 Vocational Printing Technology flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Offset lithography principle

A planographic process relying on ink-and-water immiscibility: dampening solution keeps non-image areas ink-free, image areas accept ink, and a rubber blanket transfers the image to paper.

Relief printing

A process in which the image area is raised above the non-image surface; ink sits on the raised areas and transfers under pressure. Letterpress and flexography are relief processes.

Pica and point

Typographic units of measure: 12 points make one pica, 72 points make one inch, and one point equals approximately 0.3528 millimetres. Used for type size and line length.

Halftone screening

The conversion of continuous-tone images into dots of varying size arranged on a grid, so that dot area percentage creates the illusion of tone when printed.

Total area coverage

The sum of CMYK ink percentages at the darkest point of an image. Limits are roughly 300-320% on coated stock and 240-280% on newsprint or uncoated paper.

Imposition

The arrangement of pages on a press sheet so that, after printing, folding and trimming, pages appear in correct reading order. Sixteen-page signatures are common on sheetfed presses.

Trapping in prepress

A deliberate overlap (spread or choke, typically 0.05-0.2 mm) created between adjacent colours so small registration errors do not produce unprinted white slivers.

Computer-to-plate (CTP)

Digital platemaking in which a laser images the aluminium offset plate directly from prepress data, removing film, contact frames and their associated exposure variables.

Raster versus vector

Raster (bitmap) images are pixel grids that lose quality when enlarged; vector images are mathematical paths that scale without loss and suit logos and type.

Scan resolution formula

Required input resolution equals screen ruling (LPI) multiplied by a quality factor of 1.5 to 2, then multiplied by the enlargement factor needed for final reproduction size.

Bleed allowance

Extra image or background extending beyond the trim edge, commonly 3 mm, so that cutting tolerance does not leave an unprinted white border on the finished piece.

Leading

The baseline-to-baseline distance between lines of type. Body text commonly uses leading of about 120% of the type size, for example 10 pt type on 12 pt leading.

Anilox roller

A flexographic inking roller with engraved cells that meter a fixed ink film; cell count per centimetre and cell volume in cubic centimetres per square metre determine ink laydown.

Gravure doctor blade

A steel blade that wipes surplus ink from the engraved gravure cylinder surface, leaving ink only in the cells, from which capillary action draws it onto the substrate.

Ink-water balance

The offset press condition where dampening solution wets only non-image areas. Fount pH is usually kept near 4.5-5.5 with controlled conductivity and alcohol substitutes.

Screen printing squeegee angle

The squeegee is held at roughly 60-75 degrees to the mesh; a steeper angle and higher pressure deposit less ink, while a shallower angle increases ink deposit.

Paper substance (gsm)

Grams per square metre, the standard measure of paper mass per unit area. Text stocks typically run 60-120 gsm, covers 200-350 gsm, and newsprint around 45 gsm.

Paper grain direction

The orientation of fibres parallel to the paper machine direction. Folding parallel to grain gives clean folds; folding against grain causes cracking and poor creases.

Ink tack

The stickiness or internal cohesion of an ink film. Tack must decrease through the press units so each later colour adheres to the earlier one without picking.

Ink drying mechanisms

Inks set and dry by absorption into the stock, oxidation of drying oils, evaporation of solvent or water, or radiation curing such as UV and electron beam.

Saddle stitching pagination rule

Saddle-stitched books use wire through the fold, and total page count must be a multiple of four because each sheet folded forms four pages in the spine.

Perfect binding

A binding method where leaves are gathered and glued into a square-cut spine with a cover wrapped around, suited to books of roughly 40-48 pages and above.

Die cutting and creasing

Steel-rule dies cut shapes and crease lines into board. Creasing is essential on thick coated stock, where a plain fold would crack the coating.

Foil stamping

A finishing process that transfers metallic or pigmented foil onto a substrate using a heated die and pressure, producing a reflective, raised-looking decorative image.

Lockout/tagout

Energy isolation procedure in which power sources are switched off, locked and tagged before a worker clears a jam or reaches into a press unit.

Roller setting gauge

A strip or gauge used to set the squeeze between press rollers. Inking roller contact is typically set to about 0.1-0.15 mm for correct ink transfer.

Nip point hazard

The point where two rotating rollers meet, where fingers, clothing or tools can be drawn in. Nip guards and interlocks must never be removed or bypassed.

Solvent wash-up fire risk

Press wash solvents are flammable and generate static; containers must be earthed and bonded, vapour sources kept from ignition, and waste solvent handled as hazardous waste.

Dot gain (TVI)

The difference between printed and original dot area, expressed as tone value increase at a given tint. A 50% tint commonly prints 12-20% larger on sheetfed offset.

Solid ink density

The densitometric reading of a solid ink patch, used to control ink film thickness. Typical offset targets are about 1.30-1.50 for black and 1.00-1.20 for yellow.

Print contrast

A densitometric ratio calculated as solid density minus tint density, divided by solid density, times 100. Higher values indicate cleaner highlight and shadow separation.

Break-even quantity

The output volume at which total revenue equals total cost, calculated as fixed costs divided by the difference between selling price per unit and variable cost per unit.

Udyam registration

India's MSME registration portal, which gives a small printing unit formal recognition, access to credit schemes, and eligibility for specified government benefits and tenders.