Printing Techniques PDF

Thixotropy A time-dependent shear thinning property (time dependent viscosity Certain gels or fluids that are thick or viscous under static conditions will flow (become thin, less viscous) over when shaken, agitated, sheared or stressed. They then take a fixed time to return to a more viscous state....

Thixotropy A time-dependent shear thinning property (time dependent viscosity Certain gels or fluids that are thick or viscous under static conditions will flow (become thin, less viscous) over when shaken, agitated, sheared or stressed. They then take a fixed time to return to a more viscous state. Conventional offset inks are shear thinning-they are a fairly stiff mask in an ink can, but when worked on a slab with an ink knife become fluid and free freely. Tack Stickiness of the ink, or the force required to split an inkfilm between two surfaces The first ink must be tackier than the second one, otherwise it will not transfer from the blanket Picking Occurs when the tack of the ink is greater than surface strength of paper, causing the paper to pick, split or tear How ink dries - Setting The initial phase of the drying process where the printed sheets, thought not fully dry can be handled without smudging-surface dry. How ink dries - Drying The conversion of a wet film into a hard solid state, by means of absorption, evaporation, oxidation polymerization or other Absorption Occurs whenever ink is printed on paper, dries as inks penetrate the paper. Newsprint inks use only this Evaporation Evaporation of the solvent from ink Oxidative Polymerization The reaction by which inks containing drying oils dry Oils is a presence of the drier form three dimensional chains and as they become longer, the printed ink will resist smudging on the surface Offset printing requires both absorption and oxidation to fully dry Process inks (CMYK) Are developed to have transparency, this allows the inks to overprint creating wide colour gamut Pantone inks (Pantone Matching System) Inks are developed to have high coverage, with main component being opaque. This is used to make the ink colour vivid and more saturated. Types of pantone inks Fluorescent Metallic Not all colours can be printed with process inks, and PMS colours may need to be introduced to add vibrance Specialty inks Fluorescent Metallic Magnetic Flexographic Printing A modern (conventional) relief printing process, printing using a flexible plate and liquid pourable inks. Commonly used for web printing on a wide variety of substrates (films, foils, bags, napkins) or sheetfed corrugated Application of Flexo - Very commonly associated with packaging - Often has in-line converting (die cutting, bag-making, envelope-making, cup-making, etc) - Use of spot colours (vs process) in flexo is common - Sometimes 1-2 flexo coating units are installed at the delivery end of a flexo press Construction of flexo plates Flexo plates are made using photosensitive polymer which harden when exposed to UV light Image areas are exposed to UV light, hardening the polymer, where non-image areas will be removed during processing Steps in construction of flexo plates (also refer to diagram in lecture notes) 1. Back exposure 2. Contact of negative film then laser ablation 3. Surface exposure 4. Washout 5. Drying 6. Post-exposure 7. Light finishing Flexo ink Low viscosity pourable liquid. Inks may be water-based, solvent based or UV cured. Fast drying Flexo inking system Ink pan Pan roller Anilox roll Doctor blade Plate Substrate Anilox roll Engraved cells in a ceramic-coated metal roller that transfers the ink from metering roller to the plate Need to be kept clean, do not knock them LPI Lines per inch The higher the numbers the more cells are placed in a square inch BCM Billions of cubic microns - volume of the available cells The smaller the cells the less ink each cell can carry Quality of flexo printing can be affected by the following factors: Incorrect selection of anilox - BCM/LPI Incorrect mounting tape Incorrect plate height or hardness Incorrectly exposed plate - dot shape or relief height Incorrect ink properties Ink Mixing Ink mixing for pantone inks is similar to offset Always formulate by weight (grams) not volume (mL) Volume can change depending on situation Mix base colours first, then adjust for viscosity pH, then test colour Measure for colour using densitometer / spectrophotometer Keep ink in an airtight container and shake well before use How to cite in text APA format! (author's last name, year it was published) How to cite in references APA format! author's last name + first letter of their first name, date it was published, title of article, link How to cite when its 2 authors! (author's last name & author's last name, year it was published) How to cite when its 3 or more authors! (author's last name that comes first alphabetically et al., year it was published) Oleophilic Loves oil Hydrophilic Loves water Oleophobic Hates oil Hydrophobic Hates water Lithographic Fountain Solution Is also known as dampening solution or water Used to keep the non-image areas of the printing plate clean from ink, by desensitizing the plate to ink (non image areas) Composition of fountain solution Water (95-99%) Gum arabic (as a plate preservative) Phosphoric acid (helps bind it to the plate) Buffer (to control pH) Wetting agent or IPA (reduces surface tension) Antimicrobial additives Fountain solution is made from mix concentrate or solution according to directions Normal pH and conductivity level for fountain solution pH = normally acidic pH of 3.5-5.5 conductivity = 1500 mS is ideal Dampening Solutions Tips Fountain solution must be compatible with inks, plates and substrates Fountain solution is applied to the plate by the dampening system form rollers before the plate is inked It is normal for some fountain solution to become emulsified in the ink Dampening Solutions Tips - Always print with the: Minimum ink required to achieve target density Minimum fountain solution required to keep the plate clean Fountain Solution - Related Problems Catch up, dry-up or scumming When ink is on non-image area Wavy sheets Slow ink drying - due to excessively low pH or excessive fountain solution Emulsification of ink in water, causing tinting or toner Excessive emulsification of water in ink, causing piling Construction of offset plates Aluminum or polyester (plastic plates) Light sensitive emulsion coating is hardened with exposure to light during platemaking in prepress Unhardened emulsion is washed away during processing of the plate: - Remaining hardened emulsion is the image area (oleophilic) - Where the emulsion has been removed is the non-image area (hydrophilic) Required properties of offset plates Easy to mount, adjust and remove Must be strong, dimensionally stable and uniform thickness (often.005 to.008 inches) Image areas must be as oleophilic as possible Non-image areas must be as hydrophilic as possible (Do this for better print quality) Should hold very high detail (image resolution) Image should not wear down (plate binding) despite contact with fountain solution, ink, rollers, blanket Plate life requirements can be for runs of 5000 to 1 million impressions (often baked) - if not cleaned enough Can be cleaned, stored and reused Construction of offset blankets Synthetic rubber surface with excellent printing qualities, used to transfer the image from plate to substrate Blankets have a compressible layer and a firm, smooth surface (face) The backing is a strong dimensionally stable woven canvas or other fabric Digital printing - known as non impact printing (NIP) The inked image is transferred to the substrate without applied pressure Does not have fixed image carrier (plate) Based on computer generated digital data Because there is no plate - prints can be static or variable Continuous Inkjet (CIJ) Continuously fires ink drops, with an electrically charged deflector pushing dots into the gutter for area that have no image (overall lower quality print, more waste, runs at a higher speed) Drop on demand (DOD) - Thermal DOD Electric current warms up the volatile component of the ink, causing it to burst, creating a pressure system to push the ink drop out (better resolution) Electric current (don't necessarily need to memorize but understand it) The rate of flow of electric charge past a point or region Drop on demand (DOD) - Piezoelectric DOD Electric current causes piezoelectric material to change shape, creating a pressure system to push the ink drop out. Does not require volatile components (Able to print using a variety of different inks) Drying of Inkjet Printing Inks Solvent based inks dry mostly through evaporation Hot melt inkjet inks are solid at room temperature and are heated to liquify prior to application (solid type of ink) Which inks are becoming more popular in wide format printing? UV Curable Inkjet inks Xerographic Printing A printing and photocopying technique that works on the basis of electrostatic charges (No compression because theres no plate) What is xerographic printing dominant for? (not a bottom!) It is the dominant method of reproducing images and printing computer data and is used in photocopiers, laser printers and fax machines Cannot use it for mass production (market share is less than 3%) 6 stages of xerographic printing Charging Exposure Development Transfer Fusing Cleaning Toners for Xerography Toners are pigment particles contained in a tiny bead of plastic (polymer or resin) The toner is fused to the substrate after printing using heat (substrates must be resistant to heat) Most toners are dry powders but liquid toners exist Additives improve static charge properties, flow and reduce clumping (needs to be cleaned) Xerographic toner properties Particle size typically 5-30 microns Smaller particles improve print quality but can cost more and cause dusting problems Cost and transparency of pigments can be an issue Custom (spot) colours are very limited Pigments in toners provide good fade and bleed resistance Specialty Digital Inks Metallic inks (aluminum, zinc or bronze pigments) Magnetic inks (coding of MICR bank cheques) Conductive inks (printed circuits) Scratch-off inks (rubber based with highly opaque pigment) Scratch and sniff inks (scents in microscopic gelatin sacs) Thermochromic inks (react to temperature changes) Autoclave inks (react to high temperatures) Photochromic inks (react to UV or other light) Water-developing inks (fluorescence under UV "blacklight") Security inks (indicate tampering) Fluorescent inks (for posters, advertising, labels, clothing) Phosphorescent inks (glow in the dark - light switches, clock faces, dials and advertising) Edible inks (for printing on food, hard candies, pharmaceutical tablets, cakes) Sustainability The rates of renewable resource harvest, pollution creating, and non-renewable resource depletion that can be continued indefinitely. If they cannot be continued indefinitely, they are not sustainable. The state in which demands placed on the environment can be met, without allowing people to live well, now and in the future. Sustainable development "Development that meets the needs of the present without compromising the ability of future generations to meet their own needs" - "Our Common Future" known as "Brudtland Report" By: The world commission on environment and development (WCED), 1897 Triple bottom lines - Environmental Natural resource consuming Less natural resource consumption Eco-friendly materials Reusable materials Triple bottom lines - Economic Profit & price of product Material cost reduction Logistics cost reduction (shippings considerations - you want to use the most efficient way to ship something) Three Pillars Planet Profit People Circular Economy Is an alternative to a traditional linear economy (make, use, dispose) It is regenerative by design and aims to keep products, components and materials at their highest utility and value at all times Linear Economy Make, use, dispose You don't end up at the same place where you started. Has an ending 4R Strategy - Reduce Reduce the amount of materials in weight and volume (best one to practice!) 4R Strategy - Reuse Reuse products where possible 4R Strategy - Recycle Use recycled contents increase recyclability 4R Strategy - Renew Use renewable or certified materials Life Cycle of a Product Raw Material: logging tree, mining materials, etc Manufacturing: pulping, folding, laminating, coating, printing, etc Distribution: truck trailer, train, air, ship, etc Use End-of-life (EOL): landfill, reuse, recycling, recovery Life Cycle Assessment A formal and quantitative method to assess the environmental impact of a product, process or system Best way to calculate Environmental Certification Programs (i.e FSC, SFI) Help printers to meet sustainability goals Improve best practices Provide recognition of printers with good sustainability practices Examples of environmental certification programs Forests for All Forever (FSC) Sustainable Forestry Initiative Sustainable Green Printing Partnership (SGP) Green Washing Vague and misleading claims manufacturers make about their eco-friendliness (David Suzuki Foundation) What do clients, designers and printers have in common? All want a successful print project: one which meets goals, is delivered on time and on budget (Meet the deadline! No extensions!) All want to develop relationships for future business All want to ensure the project meets the customer's requirements All want to ensure the project represents them, and their work well What unique skills does a designer bring to a job? Is the creative expert Is often the middle person between client and printer Has to consider limitations by both the client and the printing process Often decides many materials and processes: paper type, special finishes and processes, such as foils, metallics, varnishes, laminates and coatings. May decide how many colours and 4c process vs spot colour What unique skills does a printer bring to a job? Has detailed knowledge of each printing process Often has a very good relationship with paper and ink vendors, other suppliers, machine manufacturers and outsource suppliers (such as binderies) Can provide input about materials and processes, to ensure all requirements are met, including end use Can often make suggestions to control costs Is often required to satisfy the graphic designer and the client, even if the printer hasn't had much input into the design process Why do you think it is important for clients, designers and printers to communicate early in the design production process? Once the designer creates the prototype, it is very hard to go back to the design stage Discuss everything in the design production process so you won't waste time and money It increases productivity and creates less work for the clients, designers and printers !! Meet the deadline !!!