Printing is among one of the basic requirements in our daily lives, either on a small scale or larger one. It is divided into many categories which would make us easy to understand what actually it is, and what we see around us how it is made.
Small or personal level control (computer printers)
Mid level (plotters, vinyl sheet printing)
Macro level (digital, offset, bulk scale printing)
Our maximum interaction gets with the offset printing products every day. Even those who do not have an access to the personal computer printers do have an access to the offset products. The examples of offset prints are newspapers, magazines, posters, and so much around us.
In the offset printing, which we call 4 color offset print is a traditional way of printing on a mass scale especially when colors are to be involved. The three basic colors used in this method are Cyan, Magenta and Yellow. It is the percentage mixing of these colors which gives birth to so many other colors. For example, if we mix maximum percentage of cyan with magenta and yellow, very dark brown is born. That is why very dark colors especially like black are printed separately. Now the base is set, we have now 4 color separation, this is called CMYK. Normally four colors printing does not require expensive inks, only standardized inks are sufficient, but the main advantage is, that it gives an advantage of printing color photographs and other full color advertisements and figures. Due to digital technique it is possible to separate four colors and high color map printing has been made possible. This method is only acceptable and applicable when precision printing is required, that is, line separation, consistent color appearances.
Black, Cyan, Magenta, Yellow. It is not simply the different percentages of these colors; it is also the angle at which the color overlapping is done which produces other colors. Printing a map is a real test of offset printing skill.
Color mixing has either ways. It can also be done with traditional printing screens and also with special screens with randomly distributed dots, these are Stochastic Screens.
Stochastic screens are more used and preferred for the quality and precision printing.
For the stochastic screens, the frequency is variable, but for the traditional ones, the screen frequency is 60 lines/ cm.
The unwanted effects can be avoided with the traditional screens. The four color orientation maps should always use the conventional angles. In the stochastic screens, because the dots are placed randomly therefore angle are not required. The unwanted effects are technically called moir.
The appearance and the quality are dependent on the printing order. In four color offset printing, the printing order is as follows:
In traditional way, the inks are printed on top of each other. The similar way can be used to simulate the four color printing method. This would give colors and effects very close to the traditional method quite closely and similarly.
In the four color offset printing, the overprinting can be done with the following solid colors:
100 % Violet
100 % Black
100 % Brown
100 % Blue
100 % Green