Digital & Offset Printing- An Overview
When we talk about print publishing, there are two important types of printing involved they are digital print and offset print. In Laymen terms, digital printing is used for lower quantities while offset printing for bulk printing usually above thousand. In offset printing, the cost per piece/ book is much lower. Print on Demand books are printed using Digital Printing by all Publishers. The cost of digital printing is abruptly high.
Digital Printing
In this type of printing, the text or image data is fetched by the printer in digital form. A typical commercial digital printing machine can print on a 12 inches X 18 inches or 14 inches X 20 inches approx. sized paper while most inkjets print on an 8 inches X 11 inches approx. (A4) papers while heavy-duty officejets can print on higher sizes.
Digital Printing is suitable for tens to several hundred copies. Printing through a small printer at home or office is the simplest example of digital printing while they may be larger machines involved for commercial purposes. Digital printing mainly uses liquid ink or dry ink. Liquid ink is used in Inkjet Printers while the later is used in Laser Printers.
Liquid Ink consists of three components- vehicle (the liquid part), colorant (organic or inorganic particles of color suspended in the vehicle), and dryer (a catalyst added to increase the speed of drying of the ink).
Liquid Inks can be further divided into the following types-
a. Dye Based Inks: In these inks, the vehicle is water or glycol. These ink are used on surfaces that can quickly absorb the colorant to produce vibrant graphics. y are widely used in Inkjets, DeskJet, and Officejet printers. They tend to be the cheapest and most environment-friendly among all the types of liquid inks discussed here. However, they are not waterproof and can leave stains on the spillage of liquid on the printed material.
b. Solvent Based Inks: These inks use volatile organic compounds as the vehicle which are toxic and not environment-friendly. Solvent inks are durable and provide good coverage. They are not the cheapest but cost-effective. These ink are used in commercial digital printers by Spectra Polaris, Konica Minolta, etc.. Good quality solvent inks with good systems provide the best digital print with maximum durability.
c. Pigment Based Inks: These inks are the most expensive among the three and produce cutting edge long-lasting graphics. Hence, they are used in photo printers.
Dry Inks are powder inks used in toners for laser printers and many laser photocopier machines. These are the cheapest inks of all and can fade off in the future.
Offset Printing
In this type of printing, the text or image is transferred from a plate to a rubber blanket which in turn transfers it to the printing surface. As the definition suggests, these systems are extended machinery that requires power and space.
Once an offset master plate is set, it is ready to print several thousand copies of the plate. Offset machines can hold paper of large sizes namely, Demy (17.75 x 22.5 in), Double Demy(22.5 x 35.5 in), Crown (16.25 x 21.0 in), Quad (30.0 x 40.0 in), e.t.c.
Thus, offset printing is not suitable for printing lower quantities but while printing in large quantities, the cost per piece is very low.
Offset printing uses paste inks that are highly viscous (thick). The components are the same as that of liquid ink discussed above. They are delivered in canisters, unlike digital printing where the ink with all the components comes packed in a refillable or non-refillable cartridge or bottles of 50 or a few hundred milliliters. The offset inks are categorized according to the way they are cured in the printing machine.
a. Heat-Set: They are used for printing catalogs and magazines (color) and cured by firstly heating and then rapid cooling.
b. Cold-Set: These inks are directly set on the absorbing medium (the paper) without any complex heating mechanism. They are used for printing books and newspapers. this is the most economical offset option.
c. Energy-Cured: These inks are cured by the application of high energy sources like electron beam or ultraviolet rays. They are the highest quality and most expensive offset inks and machinery.
*All the discussed ink types cannot be used in the same offset machinery. An offset machine is specialized to use a specific type of ink and curing process and hence its cost.
COMMENTS
In digital printing, the cost of ink and paper can be assumed on a per-page basis while in offset printing, the cost of paper is on a per “ream” (500 sheets of a definite sized paper= 1 ream) basis and that for the ink is on a weight basis for the manufacturer. Thus, it is evident that in offset printing the cost of per piece production can be far lower than digital printing. But offset printing cannot be used for printing low quantities and in fact the minimum recommended copies are 1000 for color and 500 for b/w in offset printing.
Furthermore, be it offset or digital print, the cost of production will fluctuate depending upon the type and also the brand of the printing device or machinery, including the type and subsequently the brand of the ink and adulteration in the ink.
Notes:
*all paper sizes depicted in this article are only approximate calculations.
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The above content is an ‘extract’ from the ‘Mage Orange Publishing & Digital Marketing Magazine 2020.’ Any part of this article cannot be published, reproduced, or copied in any form whatsoever, without the permission of the publisher.
