Today I’m covering offset lithography or offset printing.
Offset uses the resistance method of printing. The basic principle of resistance printing is that oil and water don’t mix, so the same surface can be used for ink and un-inked surfaces.
Images and text are transferred to photosensitive plates (made of zinc or aluminum) photographically. The plate is then placed on a cylinder on the press. The plate obtains ink from the ink rollers, while the non-printed areas attract a water-based film (fountain solution), keeping the non-printing areas ink-free. The image is then rolled on to a rubberized offset cylinder, which in turn, inks the paper. The advantage of offset printing is the ability to print thousands of images from one plate.
Below is a side view of the offset process.

Offset Presses
There are two types of paper feeds on offset presses: sheet fed and web fed.
Sheet fed presses feed one sheet at a time through the rollers. It is commonly used for short-run jobs like brochures, letterhead, business cards, etc. Short-runs are considered less then 10,000 to 20,000 impressions.
Sheet fed presses also come in different sizes. In smaller print shops the presses are usually 2-head presses. That is that they can run 2 inks at a time. Larger print shops have 6+ head presses. These presses can run numerous inks and coatings at the same time.
Web fed presses feed off a roll of paper. Web fed presses are commonly used for large jobs like newspapers, catalogs, magazines, etc. Jobs run on web presses exceed 10,000 to 20,000 impressions. Web presses generally have 4+ heads for ink.
Spot versus CMYK
When press people talk about ink it seems to be in a strange code: of spot, CMYK, PMS, etc. What they are talking about is ink.
Spot color is a solid ink color (versus a dot-pattern of CYMK). Letterheads and business cards are the most common users of spot color.
CMYK stands for cyan, magenta, yellow and black. CMYK is also called process color. Process color creates images using a mixture of dots from all four inks. CMYK is used in magazines, brochures, etc.
PMS stands for Pantone Matching System. Pantone creates solid and CYMK inks.
Digital Printing
Since the 1990s digital printing has slowly began to replace some offset printing practices. Digital presses do not use a photographic plate. The image can be sent directly from the computer to the press, eliminating the plate and the plate making processes.
The advantages of digital presses are a lower cost in printing. Images can be changed “on the fly”. This is convenient when only one or two aspects of the image are changed. Less wasted chemicals and paper.
Below are examples of spot color offset printing:

Below are examples of process (CYMK) offset printing:

Hope you enjoyed this little snippet about Offset Printing, next up Screenprinting.
Just Hit Print… Screen Printing
Posted in Etsy, Information and Commentary with tags art, clothing, Etsy, gocco, ink, posters, print, printing, screen print, screenprinting, serigraph, silk screen, silkscreen, versatile on October 20, 2009 by kellyjcallahanToday I will be covering screen printing. Screen printing is also known as silk screening or serigraphy.
Screen printing is one of the earliest methods of printing. It has been around since approximately the Song Dynasty in China (979 t0 1279 AD). Screen printing involves the passing of ink or any other printing medium through a mesh or ’screen’ that has been stretched on a frame after a stencil or design is added to the screen. The stencil determines what will be imprinted and what will not on the printed surface. A roller or squeegee is drug across the screen stencil, forcing ink past the threads of the woven mesh in the open areas. Like offset and lithography, for every ink color used a screen is needed.
Below is a simple screen print process.
Creating the Stencil
There are several methods for creating the stencil.
Screen Printing Inks and Materials
A multitude of products can be used on a screenprint.
Versatility
Because screen printing can be done on a variety of substances, it is one of the most versatile printing processes. Screen printing can be done on clothing, textiles, labels, electronics, circuit boards, balloons, medical devices, snowboards, signs and displays.
Gocco
Gocco (go-ko) is a form of screen printing that originated in Japan.
Gocco is a self-contained compact color printing system that uses flash bulbs to thermally imprint and image on a screen. Because the printing system is compact, only small images can be created.
Gocco’s are easy to use; simply load the art, a blank screen, and sometimes a special filter into the machine, use the bulbs to burn the image into the screen, ink the screen, and print.
Below is an image of a Goco kit.
Screen Print Examples
Gocco Examples
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