Sheetfed Lithography is a crucial component in almost every marketing promotion. After 90 years Sheetfed Lithography is still making history. Sheetfed Lithography is also known commonly as Offset Printing. It is the technique of transferring an inked image from a rubber blanket then to the printing service. When used with the Lithographic process, it employes a flat image where the printed object obtains ink from the printed rollers. The non-printing area creates an attraction to a water based film called "fountain solution" keeping the non-printed areas ink free. The offset Print came to life in two versions: in 1875 by Robert Barclay from England, and in 1903 by Ira Washington Rubel.

Advantages..


- The images are high quality, type more easily than a letterpress printer
- Quick production of printing plates
- Its the cheapest method of producing the high quality printing

Disadvantages


- Slightly less quality compared to rotogravure or photogravure printing
- It takes a long time to set up and less jobs are moving to digital offset machines

It can print on both sides of the paper in one pass, apposed from just one side. Web-fed are faster and makes them more ideal for newspapers and magazines but Web-fed have a fixed cut-off.

Process

The most or one of the most important processes is called Pre-press Production. Pre-press makes sure that every file is correctly in line and ready for printing. It includes converting to the proper CMYK, finalizing the files, making sure all the colours are ready to be run on the press. The sheet-fed press actually consists of different systems that all work together to complete the process.. Feeder system, printing system, inking/dampening system, and the delivery system.

Types of Platemaking

Most of the time the plates used in offset printing are thin, basically all made out of aluminum, but sometimes can be made out of multi-metal paper or plastic. Sometimes you can also used polyester plates in place of aluminum plates, for smaller or medium quality jobs.

Types of Chemicals Used

The ink that offset printing uses is usually very thick and viscous. It HAS a wide variety of inks so it wont be hard to find a kind of ink to use for a specific print. Some of these include heat set, cold set, and energy curable.

The largely used type of ink is letter set ink.
Single Fluid inks are a new type of ink and they allow lithographic plates on a lithographic press to print without using a dampening system.

Water and Ink are very important part in the offset printing process. If the water and ink are not balanced in the proper way there is a variety of problems that can affect the quality of the finished product. Some problems range from scumming, catchup, trapping problems, ink density etc...

Fountain Solution

Fountain Solution is water based and the component in the life of the graphic process that dampens the non-imaged area of the plate, in order to keep ink from depositing. They used to be acid based but then figured out alcohol and water makes the water more wet. This helps cool the press and ink stays stable to ink can dry fast . Acid based fountain solutions are stil the most commonly used variety because of superior protection of the printing plate, lower dot gains, and longer plate life. Acids are also compatible of running with every type of offset litho inks. There also the most expensive to produce.