PRINTING TECHNOLOGY

Printing Inks Ink Ingredients Ink ingredients fall into three main categories: pigment, vehicle, and modifiers/additives. Because there are so many different types of printing processes and print applications, the ingredients used in these three categories may vary widely. For example, for offset lithography, ink requires a higher degree of pigment than many other processes. This is because nearly half of the ink used in the offset process does not reach the printing surface. In direct printing methods, such as letterpress, a much higher percentage of the ink reaches the substrate. Pigment The ingredients that comprise the color of the ink are referred to as pigment. The pigments are formulated from substances that create a desired color when the substances are blended together in specific proportions. Some of these substances may be ingredients found in nature or they may be produced synthetically. The substances can be in the form of dyes, powders, liquid dispersions, or concentra...

• Printing inks dry by different mechanisms depending on the printing method.• The common methods are penetration (absorption), oxidation, setting, evaporation and polymerization. Normally the drying is a combination of above mentioned methods. • How the ink dries by different printing methods: Sheet-fed offset : : By oxidation and absorption Heatset: : By evaporation of solvent . Offset/UV-ink : Polymerization Gravure: evaporation Flexo: evaporation Drying of the Ink – Sheet-Fed Offset Printing • Sheet-fed offset inks dry by oxidation and by absorption. The ink pigment is dispersed in medium that is a mixture of oil and resin (resin dissolved into oil). The resin stays on the top of the printing ink layer and covers the surface of oxidized oil. The solvent of printing ink penetrates into the paperboard pores. The resin hardens and the surface of printed layer gets touch resistant. After the ink has set the oxidation and further on drying can begin. The ink layer gets harder and...

Preventive quality control is before-the-fact action utilizing quality control procedures to prevent problems before they occur and thus minimize downtime and waste. Quality control procedures are succesful when they are in sync with maintenance planning, continuous productivity improvement programs and business align ment strategies. Total Production – and Prepress – Maintenance (TPM) concepts integrate with those of Preventive Maintenance (PM) and Total Quality Management (TQM), aiming at zero breakdowns. Apart from any formal certification program, print consistency can largely be obtained by adherence to standards as defined in the ISO 12647, “Graphic technology – Process control for the production of half-tone colour separations, proof and production prints”. 1. Viewing Conditions The pressroom’s light levels must be high enough around the press to permit press crew to install plates, blankets and packing easily and to make press adjustments without eye strain. Having a light shi...

PRESSMAN TIPS  Packing and cylinder pressure seem to be the number one culprit in printing related problems. It is absolutely necessary for the press operator to check and maintain proper printing pressure between plate, blanket, and impression cylinders. Press manufacturers should be able to supply this valuable infor mation. Most of the time the packing information is located on a plate on the press or in the operating manual. How much pressure is too much? Most operators feel that is .004" squeeze is good, then .008" must be better, and if that doesn't work then an extra .002" - .004" will certainly help. This will without a doubt effect quality and production. Most presses should operate with .004" - .006" squeeze between cylinders. Any more than this can cause problems like dot gain, emulsification, bearing shock marks (streaks), poor register and fit to name a few. It would take several paragraphs to explain how each one of these problems ...

Surface energy is a fundamental property of solids and varies from low in plastics such as PE to high for glass and metal surfaces. Surface tension is the analogous property of liquids. For a liquid to wet the surface of a solid, its surface tension must be lower than the surface energy of the solid. The equilibrium value is known as critical surface tension (CST). Contact angles of the liquid/solid interface often are used as a measure of wetting, with lower values indicating better wetting. The phenomenon of wetting in our industry is the property of a liquid-solid system, typically water-based ink, primer, lacquer, and adhesive as applied to plastic films. Organic solvents used in solvent-based products assure good wetting of commonly used plastic films. They have surface tensions of 20-24 dynes/cm, which is well below the surface energy of packaging films such as LDPE, OPP, and PET. Almost without exception, solvent-based products lay down smoothly on packaging films — a required ...

Ink mileage is usually defined as the number of copies produced with a kilogram of ink, or more commonly quoted in the newspaper industry as the kgs of ink required to print a thousand impressions on paper. . Estimating ink mileage has always been a difficult task. This is because there are several interest ing factors that control the amount of ink required to achieve the final ink density. The factors that most influence the ink requirements are as follows: 1) Strength of the ink 2) Substrate 3) Print Density Control 4) Ink and Water Balance 5) Print coverage Strength of the ink The key factor here is the level of pigment in the final ink formulation which determines how much ink is required to achieve density. The pigment is the ingredient in the ink that either absorbs or reflects light. When ink is printed on paper, what we are trying to do is to change the light reflection off of the paper so that the reader perceives color. The pigment type has certain characteristics to ...

Digital-Positioning Water Transfer Printing Technology:- Increased standard of living brings about a new level of needs from discerning consumers today. Apart from the utilization value of a product, consumers demand the aesthetic value attached to it. This presents an opportunity to surface treatment to place a part i n this value adding role. The digital-positioning water transfer printing technology allows a plain surface of a product to be transformed immediately into colorful one. Normal printing technology only work best on flat product surface; products with irregular surfaces would encounter a high degree of production defects in printing; however with the development of Digital-positioning water transfer printing technology; challenges faced by conventional printing technology ...such as offset printing; screen printing; thermal printing could be effectively overcome. Digital-positioning water transfer printing technology is an extension of Dye-sublimation. It employs...

 Backtrap Mottling is mostly frequently seen in the ink printed in the first or second printing unit of a multicolor offset printing press. The cause lies in the partially absorption of ink into the paper.  The partially variable immobilization of the ink leads to a variable splitting of the i nk on the blankets. An uneven (thicker/thinner in various areas) ink film remains on the paper surface, which the human eye sees as mottled. The partially variable ink absorption is configured differently on each of the following sheets, as a result of which the mottling effect increases rather than diminishes as experience shows.                               Backtrap mottling can be triggered by an uneven formation which could be in the base paper stage and/or by a binding agent migration during the applied coating.     ...

Water pickup is probably one of the most controversial and misunderstood ink characteristics. The numbers obtained on water pickup and the resulting curves plotted from this data are open to a wide range of interpretations. Nevertheless, printers and inkmakers insist on conductin g this test and trying to predict an ink's performance based on water pickup values. The reason? The idea of a water pickup value seems to make sense. In lithography, whether web or sheet-fed, water or dampening solution wets a plate's non-image areas, preventing ink from transferring. Meanwhile, image areas repel water but attract ink, thus producing the image. To ensure sufficient wetting, a surplus of water is supplied to the plate surface. The more skilled the printer, the less the amount of water applied; nevertheless, water always is left over and must go somewhere. Paper absorbs some, and a certain amount of evaporation occurs, but a large quantity also is taken up by ink. The surplus dampening...

Printing standards and their associated specifications bring an independent, authoritative, and concrete basis for file preparation, proofing, presswork, and output evaluation. They reduce proofing cycles and enable faster approval processes. They also help synchronize expectations between print buyer and print provide r. I'll begin with a few definitions. A Standard according to the International Organization for Standardization (ISO) defines a standard as: "A document established by consensus and approved by a recognized body that provides for common and repeated use, rules, guidelines or characteristics for activities or their results, aimed at the achievement of the optimum degree of order in a given context." A Specification is not a standard. Rather, it is a detailed description of the criteria for a piece of work. Specifications for printing can include characterization-data, ICC-profiles, PDF preflight criteria, calibration targets for the print proces...

Here is an old saying that oil and water don't mix, however in lithography if  the two don't properly mix, you will not be able to print. In order to make  the system work, you need a proper marriage among all the variables. All  lithographic inks need to emulsify fountain solution in order to work  correctly. If a lithogr aphic ink did not emulsify fountain solution, the ink  would not even transfer to the plate. Too much emulsification will result in  scumming, too little will cause water marking. In the lithographic process,  the plate is composed of two different types of areas. The non-image is a  water loving area (hydrophilic) while the image area is oil loving (oleophilic) . While this means that the water or oil will preferentially like one area  greater than another, it does not prevent the water phase from going to the  image area. The fountain solution for instance will wet o...