There are a couple of standard procedures for creating wall murals using decals.
The Cost-effective Printing
If you need hundreds or thousands of wall decals printed, then it will probably be the most cost-effective to screen print them.
Screen printed decals have been around for many decades, and range in size from very small to quite large, but for the purposes of this conversation, we'll use a 4' x 8' size to demonstrate how the screen printing process works.
If your graphic is a "4CP" (four-color process) print, or full color decal, it has to go through a process called "color separation." We take the digital file (rarely do we work from a photograph like we did 20 years ago) and put it through a specialized software that separates the four colors into 4 different files for the four colors used in 4CP or CMYK printing.
CMYK are the color codes in the 4CP printing that stand for Cyan, Magenta, Yellow, and Black (not quite sure who decided "black" started with a K).
Once the files are separated, films are created from each file and are sent to the pre-press department, where they are taped to an emulsion-coated "silk" screen (actually made from nylon in the modern era, for the most part), loaded into a vacuum frame, and exposed to light for a pre-determined amount of time (depends somewhat on the type of exposure unit, the age of the lamp, etc.).
Once the screen is exposed, it is immediately sent to an exposure area (some shops do it manually, others with specialized exposure units) and the non-exposed areas are washed out. The washed out areas are the areas that the ink will be pushed through during the printing process.
Once the screen is dry, it is now ready to be loaded into the press and lined up to the substrate for printing. Typically, the first color down is yellow, then magenta, cyan, and finally black (print from light to dark).
Most shops now use UV inks which are cured using a set of UV lamps set over a conveyor belt. This is especially useful with decals as they lack rigidity, and so when they come off the belt, they're completely dry and ready to stack to send back around for the second, third, and fourth colors to be printed.
Short Run Digital Printing
The other main way of printing decals has been around a couple of decades now and has supplanted screen printing to a great degree, but has also opened up a new market - short run large format decals. Most digital decal media is around 54" in width, although there are wide format printers that go up to 16'. If you're creating a wall mural, most print shops will panel the prints so they can be installed like wall paper, in strips about 48" in width and a long as the wall is tall.
The process to print wall decals is much simpler with a digital printer. Take a color file, run it through the RIP software, and send it to the printer. Pretty much that simple. Digital printers are also getting faster. There are printers that can put out the equivalent of 200+ 4' x 8' sheets per hour, and it may be that within another few years, screen-printing could become obsolete.
ABOUT THE AUTHOR
Barry K. Brown has been in the Sign, Banner, Decal and Display Business for over 20 years. It isn't what he thought he'd do with his life, but he says he knows too much now to do anything else! Barry is a great resource for information regarding Signs, Banners, Decals, and Displays, and is also an outstanding source of information on how to shop online without getting ripped off.
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