Pancyprian TS Graphic Arts III Θ.Κ. cheat sheet

Offset lithography uses planographic plates; ink adheres to image areas and is repelled by water in non-image areas, transferred via a blanket cylinder to the substrate.

Flexography uses elastomeric or photopolymer relief plates and low-viscosity solvent/water-based inks; typical anilox roller cell volumes control ink film thickness.

Gravure engraves cells into a copper cylinder (often chrome-plated); doctor blade removes surplus ink, and cell depth/area determines tone; suited to long runs and smooth substrates.

Screen printing forces ink through a mesh stencil with a squeegee; achievable ink deposit is high (typically 10–100 µm), enabling opaque whites and specialty effects.

Digital printing (inkjet, toner) is plateless; variable data is possible, but per-sheet cost is relatively flat while offset/flexo/gravure benefit from run-length economies.

Key process selection rule: run length, substrate, image quality, and ink film thickness requirements determine process; offset dominates commercial print, flexo packaging, gravure long-run packaging, screen textiles/glass, digital short-run/personalised.

Ink transfer in offset relies on ink-water balance; excessive dampening causes emulsification, poor ink transfer, and mottling; insufficient water causes scumming.

Halftone screening converts continuous tone to dots; AM screening varies dot size at fixed spacing, FM (stochastic) varies dot frequency at fixed small size; hybrid combines both.

Image capture: input resolution should be set so that final output resolution at 100% size is typically 300 ppi for offset; scanning at higher than needed resolution wastes storage without quality gain.

Colour separation converts RGB to CMYK; UCR/GCR control black generation and ink limiting; total area coverage (TAC) is usually capped around 300–340% for coated stock, lower for uncoated/newsprint.

RIP (raster image processor) interprets PostScript/PDF and renders it to a raster at device resolution; it handles trapping, screening, and colour conversion.

CTP (computer-to-plate) images plates directly via laser; eliminates film, reduces dot gain, and shortens make-ready; plate type (thermal, violet) must match imager wavelength.

Imposition arranges pages on a press sheet so that after folding and trimming pages fall in reading order; key calculations: pages per sheet = (number of sides) × (rows × columns).

Workflow standards: PDF/X-1a (CMYK or spot, no transparency), PDF/X-4 (supports transparency and ICC), and preflight checks for fonts, bleed (typically 3 mm), and colour space.

Trapping (spread/choke) compensates for misregistration between adjacent colours; typical trap width 0.1–0.2 mm depending on process and substrate.

Proofing: contract proof must simulate final output colour and substrate; soft proofing requires calibrated monitor and accurate ICC profiles.

Additive colour (RGB) combines light; subtractive colour (CMYK) combines inks that absorb light; RGB is device-dependent for displays, CMYK for printers.

Primary subtractive inks are cyan, magenta, yellow; black (K) is added for density, text sharpness, and reduced ink cost; CMY alone cannot produce a neutral dense black.

ICC profiles characterise device colour response; a source (input) profile plus destination (output) profile with a rendering intent (perceptual, relative colorimetric, absolute colorimetric, saturation) governs conversion.

Relative colorimetric preserves in-gamut colours and maps white point; perceptual compresses the whole gamut to preserve relationships; absolute colorimetric preserves exact colorimetry including paper white.

Densitometry measures ink film optical density; solid ink density (SID) targets vary by ink and substrate; dot gain (TV) is difference between measured and requested dot area.

Spectrophotometry measures spectral reflectance and computes CIELAB values; ΔE (e.g., ΔE00) quantifies colour difference; ΔE < 2 is typically visually acceptable for many print applications.

Spot colours are pre-mixed inks (e.g., Pantone) printed as additional separations; they extend gamut beyond CMYK and ensure brand consistency; they require separate plates and ink ducts.

Colour management workflow: calibrate and profile devices, embed/source profiles, soft-proof, convert with intent, and verify with measurement against target tolerances.

Type classification: serif (old style, transitional, modern, slab), sans serif (grotesque, humanist, geometric), script, and display; each has different stroke contrast and legibility characteristics.

Measurement systems: 1 point = 1/72 inch (PostScript) or approximately 0.3528 mm; 12 points = 1 pica; type size is measured from ascender to descender in metal type, but digital em size differs.

Leading (line spacing) is measured baseline-to-baseline; typical body text leading is 120% of type size (e.g., 10/12).

Tracking adjusts overall letter spacing; kerning adjusts spacing between specific pairs; both affect readability and colour of text block.

Grid systems (baseline, column, modular) provide consistent alignment; margins, gutters, and live area define the text block; rule of thirds and golden ratio are composition aids, not requirements.

Hierarchy is created by size, weight, colour, and position; contrast and white space improve legibility; avoid too many typefaces (typically 2–3 per job).

Widows and orphans are single lines at the top or bottom of a column; avoid by adjusting leading, tracking, or copyfitting.

Paragraph alignment: justified text requires hyphenation and can create rivers; ragged right avoids rivers but creates uneven right edge; centred and asymmetric alignments suit display text.

Grammage (gsm) is mass per unit area; common office paper 80 gsm, coated art paper 130–170 gsm, board 200–400 gsm; bulk = thickness per unit grammage.

Paper grades: uncoated (bond, offset), coated (gloss, matt, silk), recycled, newsprint, and specialty; coating affects ink absorption, gloss, and dot gain.

Ink types: offset litho (paste), flexo (liquid), gravure (liquid), screen (paste), UV-curable, and digital toner/inkjet inks; each dries by different mechanism (absorption, oxidation, evaporation, UV curing).

Drying methods: oxidative (linseed oil), evaporation (solvent/water), penetration (porous stock), and radiation curing (UV/EB); insufficient drying causes set-off and blocking.

Ink tack and viscosity must match substrate and press speed; high tack can pick uncoated paper fibres; low tack may cause poor transfer.

Paper properties affecting print: smoothness, porosity, absorbency, opacity, brightness, and grain direction; grain direction affects folding and dimensional stability.

Finishing stocks include laminating films (BOPP, PET), varnishes (aqueous, UV), and adhesives; compatibility with ink and substrate must be tested.

Moisture content of paper (typically 4.5–6%) affects dimensional stability; conditioning to pressroom temperature and humidity reduces misregistration and waviness.

Cutting: guillotine cutting calculates lift height from paper bulk; clamp pressure and blade sharpness affect cut quality; trim marks and bleed ensure clean edges.

Folding: parallel, cross, and gate folds; fold direction relative to paper grain matters-folding parallel to grain reduces cracking; score or crease heavy stock before folding.

Binding methods: saddle stitching (wire through spine, for booklets), perfect binding (glued spine, for thicker books), spiral/wire-o, and case binding; page count and paper weight determine choice.

Laminating applies a film to the printed surface using adhesive and heat/pressure; matt, gloss, and soft-touch finishes affect subsequent processes (e.g., foil blocking may not adhere to some laminates).

Die-cutting uses a steel rule die to cut, crease, and perforate; make-ready includes packing to compensate for cutting force; nick connections hold parts in place.

Quality control: check trim size, fold accuracy, registration, colour against proof, and binding integrity; use control strips and sampling plans (e.g., AQL).

Foiling and embossing require heat and pressure; embossing uses male/female dies; foil adhesion depends on substrate and size of image area.

Numbering, perforating, and punching are secondary operations that must be planned in imposition to avoid extra passes.

Hazardous substances in print include solvents (VOCs), inks, fountain solutions, plate developers, and cleaning agents; safety data sheets (SDS) must be available and understood.

COSHH-type assessments (or local equivalent) require identifying hazards, exposure routes, and control measures; PPE (gloves, goggles, respirators) is the last line of defence.

Machine guarding: all nip points, gears, and rotating cylinders must be guarded; interlocks prevent operation with guards open; lockout/tagout during maintenance.

Waste hierarchy: reduce, reuse, recycle, recover; print waste includes paper trim, ink containers, solvent rags, and plates; segregate hazardous waste (solvent-contaminated rags) from general waste.

VOC emissions are controlled by extraction, low-VOC inks, and recovery systems; local exhaust ventilation at solvent use points is essential.

Noise and ergonomics: pressrooms can exceed 85 dB(A); hearing protection and noise reduction required; manual handling of paper stacks requires training and aids.

Fire safety: solvents and paper are combustible; store solvents in fire-rated cabinets; ensure extinguishers and emergency exits are clear.

Environmental management: FSC/PEFC chain-of-custody for paper, energy-efficient presses, and water-based inks reduce environmental impact; register of regulations and permits must be maintained.

Sheet count for a job: number of sheets = total pages / pages per sheet; add waste allowance (typically 2–5% for offset, higher for short runs or complex finishing).

Imposition arithmetic: pages per sheet = sides × (rows × columns); for a 16-page signature on a 4×2 layout with 2 sides, pages per sheet = 2 × 8 = 16.

Paper weight calculation: weight (kg) = area (m²) × grammage (g/m²) / 1000; ream weight = sheet area × gsm × number of sheets / 1000.

Costing: total cost = paper cost + ink cost + plate cost + press time + finishing + waste; cost per unit = total cost / net quantity.

Ink coverage estimation: total area coverage (TAC) and percent coverage per colour; ink cost per 1000 sheets can be estimated from coverage and ink price.

Run-length break-even: compare digital vs offset using fixed setup costs (plates, make-ready) and variable costs per unit; break-even quantity = (offset setup − digital setup) / (digital unit cost − offset unit cost).

Waste allowance formula: gross sheets = net sheets × (1 + waste %); for example, 10,000 net with 3% waste requires 10,300 sheets.

Time calculations: press speed in sheets per hour (SPH); run time = sheets / SPH; add make-ready time and downtime allowance for scheduling.