How does 4-color printing (offset) differ from 1-color?

Question

Any shed light on the subject is greatly appreciated !
So (as far as I understand) for 4-color offset printing, when say a photograph is printed, 4 colors (CMYK) are applied sequentially to the same area (in different amounts) to achieve the desired color. Now, is it possible to achieve the same 4-color process, by using say 1-color press and then running the same job 4-times (4 plates), one for each color?
Thanks ahead for any help!

Answer 1

It CAN be done, as you describe. Although not an offset printing process, this is exactly how multi color silk screening is done. Instead of plates, four different screens are cut, one for each color.



The difficulty is in what is called "registration." Each subsequent color needs to be applied in a very careful alignment, so that the "blended" colors come out properly, and the different objects of the design line up properly. It wouln't do, for instance for the blue pupil of an eye to line up outside the outline of the eyelid. That's why in real offset printing, the entire job is run on a single press, with the four color plates perfectly aligned.



It's a lot more complicated than that because the colors are not exactly blended on the paper. Dots of pure Yellow, Magenta, Cyan and Black are place in discrete patterns, close together, and in carefully sized dots. It is the eye, looking at the printed page that "blends" the color in the viewer's mind.



I always recommend that a serious design student take the time to learn and understand print technology. The more the designer knows what happens in the post design process, the better he can create a designt that does what the client expects. PLUS, in my case, as a freelancer, I am more able to do on my computer that would otherwise have to be done by a technicial down the line. That way I get paid to do the work instead of the client having to pay the printer to do it for him. I have the capability to do my own color seps, traps, chokes, bleeds, etc. When I send a file to the print service bureau, it tends to go straight to "plate" and immediate printing.



Your question is a great example of what a designer should know. For that, I'm giving it a star rating.

Answer 2

Four color press printing is called offset. Different areas of the stock are printed with different colors. (offset) There is never more than four colors. because with four colors, no two adjacent areas will ever be the same color. I've never heard of sequential printing in the same area because it would contaminate the plates.



The sequential printing you outlined is used in silkscreen and ink-jet printing except the print area is only "sprinkled " with the color in slightly different positions. This causes the eye to see it as a blend color of a different hue.



To do what you suggest would require each color be dried and I'm not sure if you would come out with color you want. Some inks are transparent and others are opaque. You would have to know what to use where.

Answer 3

Many years ago I was a part-time commercial artist for a while, and I hung around with the printers a little to get the job run right, and picked up a little bit of printing knowledge along the way.

I used to ask the printers "Can this be done?" And their standard response was "We can do anything if you can afford it." Then they would suggest the best looking, cheapest price method for the particular job.



Four color offset is a printing method that is extremely fast for huge runs. For example Web presses can run press speeds can reach up to 50,000 impressions per hour. An impression is equal to one full press sheet (38 inches x 22 and three-fourths inches), which is 12 pages. That's six hundred thousand pages an hour. That is how Newsweek or Time can print millions of magazines in a week. because the plates do not touch the paper they do not wear out after so many impressions. I have seen web presses running so fast that the friction of the paper running through the presses creates so much heat that the speed is limited by the kindling temperature of the paper. The humidity is controlled exactly in big offset printing houses to allow for perfect paper/ink/press speed happiness.



However, the time and cost associated with producing offset plates and the offset printing press setup makes smaller quantity printing jobs impractical. As a result, smaller printing jobs are now moving to digital offset machines.



Since four color offset printing is designed for speed in producing large runs that is what they should be used for.

You would lose speed, and increase costs if you had to remove and reload the paper for each color. And re-registration (lining up the paper exactly so the tiny dots match up perfectly) would be a nightmare task.

Printing each color sequentially in a very short run is better suited to say, silk screen, or lithograph.

More and more printing stuff is just going to high speed digital copy machines where the limited size of the small run is immaterial to the set-up costs. Artists can do a lot of the set up stuff on computers that we designers used to have to depend on the printers to do. It gives us more immediate creative control and freedom.



Short four-color offset printing video:

http://computer.howstuffworks.com/offset-printing.htm



Color silk screen printing:

http://en.wikipedia.org/wiki/Screen-printing



Lithography:

http://www.lib.udel.edu/ud/spec/exhibits/color/lithogr.htm



Color Lithography in art prints and posters:

http://www.art.com/asp/customerservice/limitededitionfaq-asp/_/posters.htm



So, OhWhyDontIknowMath, in theory you could print one color offset, then remove the paper after the first color, reload the paper, (being careful to get prefect alignment for perfect color registration) Then print the second color, remove, reload, register and run again for the third color, then print, remove, reload, register and run again for the last color.

Too labor intensive, expensive, and slow. Do the math!

You'll see that that would defeat the advantages of four color offset machines that are built for super high speed printing of huge runs at amazingly fast speeds.



Here is a quick, down and dirty explanation of what happens and why:

The colors of the image are photographically "filtered" into tiny dots (called "benday dots.)" See the explanation here:

http://en.wikipedia.org/wiki/Halftone

These benday dots line up in perfect "registration" (alignment) and the eye blends them together to give the illusion of a continuous color tone in the printed picture.

Different kinds of printing techniques have different advantages and disadvantages. So you have to pick the printing process that best meets the particular demands of the specific job.



Could a race car haul dirt?

Yes, but not as well as a big and slow, pickup truck.



Match the needs of the job with the capabilities of the method.

Answer 4

Yes, technically you could do as you ask, use a press with one plate, and switch out the plate and run it with the 4 inks. However, with all presses, the plates always need to be registered, or aligned, so that the colors overlap properly. So you would never get a proper print with a single stage printer, and I don't think you could even find a printer who runs such a press.



Mike Malaska

http://www.mikemalaska.com

Answer 5

Black and colour