Have you ever found it confusing about how one printing process differs from another? Most printing that account managers will arrange will be either offset or digital printing, but every so often you will receive a project that will challenge your production knowledge. Here are some printing tips that could help you sound knowledgeable when everyone else looks blank.
Chart courtesy of BJ Ball Papers, New Zealand
Usually referred to as "offset", it is called such because the inked image is "offset" (or transferred) from a plate (usually metal, though can be polyester) to a rubber blanket, then onto the printing substrate.
"Lithographic" printing is based on the principle that oil and water don't mix. On the flat metal printing plate, the image area attracts the ink from the ink rollers, while the non-printing areas attract a water-based film (fountain solution), keeping the non-printing areas ink-free.
Offset printing is used to produce a huge range of long-run printed work, such as brochures, stationery, newspapers, magazines and direct mail.
There are two main categories of offset printing: sheet-fed and web-fed.
Sheet-fed uses paper pre-cut into sheets and fed into the press via a suction bar. Sheet-fed printing is commonly used for short-run magazines and general commercial print jobs.
Web-fed uses a roll of paper (a "web"). Offset web printing is used mainly for runs in excess of 5,000 or 10,000 impressions. Typical examples of web offset printing includes newspapers, newspaper inserts, magazines, catalogues and books.
Also known as "relief printing" letterpress is the oldest of printing methods. Founded by Gutenberg in 1440, relief printing means the images on the plate are higher than the surface (like a rubber stamp). The press operator composes and locks movable type into the bed of the press, inks it up, then presses paper against it to transfer the ink from the type onto the paper.
Other forms of relief printing include wood engravings, zinc plates and linoleum blocks.
Though not common these days, letterpress machines still produce fine, artisanal work and die cutting.
Flexography is another form of relief printing, but this time using plates made of rubber or photopolymer. "Flexo" (as it is affectionately termed) is a web printing process, and is used mainly for printing packaging products and non-paper substrates (such as plastics, food wrapping, foil, etc) and reel-fed labels.
Also known as "intaglio", gravure printing is ideal for ultra-high run print jobs such as magazines, newspapers, direct mail catalogues and packaging. It can also be used for upholstery and textiles, wallpaper and postage stamps. The process can produce extremely fine, detailed images, making it a process of choice for fine art reproductions.
The image to be printed is etched onto the surface of a metal plate or cylinder. The image is in the recesses (or depressions) not the raised part of the plate as in relief printing. The recesses are filled with ink and the raised portions are wiped or scraped free of ink. The paper or substrate is then pressed against the inked plate or cylinder and the image is transferred.
The plates and cylinders are highly expensive to produce, and gravure printing companies are few and far between.
Engraving produces the sharpest image of all the processes. Steel dies are cut or chemically etched to hold the ink. Paper is forced against the plate under pressure, creating an embossed or raised impression.
Before the advent of photography, engraving was used to reproduce artwork (e.g. in newspapers and books) and is used today primarily as an art form. Some countries still use engraving to produce their postage stamps and paper currency.
Also known as silkscreen, serigraphy and serigraph printing, screen printing is more than just useful for printing t-shirts. Screen printing is employed for a variety of projects including packaging, posters, art works onto canvas, balloons, signs, displays and stickers, and is in its element when printing onto non-paper substrates such as textiles, vinyl and wood. The surface does not have to be printed under pressure, which gives screen printing a distinct advantage over other printing techniques.
The printing technique uses a woven mesh screen to support an ink-blocking stencil to receive a desired image. A squeegee blade is moved across the screen stencil, forcing ink into the mesh openings. The ink will pass through the image areas and will be blocked in the non-image areas.
In recent times, screen printing is being superseded by large format digital printing processes for some substrates and projects.
Thermographic printing is your go-to process if you want raised printing. It uses special powder that adheres to any colour ink and relies on heat to create the letters or images on a sheet of paper.
There are three sections in a thermography machine: The first section applies the thermographic/embossing powder and the areas to have raised printing are inked. The second section is a vacuum system that removes excess powder from uninked areas of the substrate. The third section is a radiant oven with temperatures of 480˚C (900˚F) to 700˚C (1300˚F) which raises the inked areas.
Thermographic printing is commonly used on wedding invitations, letterheads, business cards, greeting cards, gift wrap and packaging, and can also be used to print braille text.
Digital printing is the newest kid on the block. The term encompasses many different types of printing from toner-based laser printing to ink-based solutions, such as inkjet printing.
Digital printing is ideal for short-run projects, and projects which require personalisation of words and/or images (using variable data printing).
Some digital presses have the speed and image quality output to rival offset as the preferred printing method, and can offer competitive pricing for medium print runs.
Digital printing does not require plates, and is ideal for fast turnaround, print-on-demand jobs.