| By :
Stewart Wrighter
The list of Prepress equipment includes items such as ECRM Plate Setters, Mac and Windows operating systems as well as Canon and Epson digital proofing systems. CTP (computer to plate) is an imaging or prepress technology that is used in modern lithographic printing work. Such technology can be used in desktop publishing to output images directly to a printing plate. Litho is a term that is widely used today in the printing industry. This is a Greek term meaning "stone". Originally, lithographic printing was first discovered way back in 1798 by a person called Alois Senefelder. From that time on till the present, lithographic printing has grown to become very popular among commercial users as well as artists. When Senefelder first discovered this form of printing he used a number of steps which have since been modified and adapted as well as innovated to become the modern lithographic printing that we see being used by almost every printing business. Graining Graining is the first step in modern lithographic printing. Litho stones are normally sourced from Germany where there are special limestone quarries that provide litho stones that have to be grained after each use. After the stone has been grained and it is made fit for the image, artists must then pick on an image that they wish to create. In this regard, they will need to start off by drawing a basic outline of the final image. This outline is normally created on tracing paper. Artwork Once the line drawing has been completed it must then be traced onto the stone with the help of a sheet that has been smeared with some iron oxide powder that doubles up as a carbon paper. Use of iron oxide helps to leave a red colored outline on the stone which the artist can use as a guideline to complete the image on stone. When making multi-colored images, this work can become very complicated because each color must be drawn separately on the stone. Chemical processing Perhaps the most difficult part of litho printing is the chemical processing which is also a fundamental aspect to proper litho printing. This is because lithography makes use of a single surface area for both the image as well as non-image areas. To separate the two areas, it is necessary to use chemical processing which in turn requires etching with the help of a gum Arabic solution mixed with nitric acid. The Actual Printing After the chemical processing stage has been completed the stone must then be printed with ink of a color in which the image is to be printed. Once this ink has been applied, a sheet of paper will have to be laid face down on the stone. Over this, a sheet of plexiglass or a tympan will need to be placed. After that, the press bed will be moved horizontally until the scrape bar is lowered on to the tympan. The image will then be printed as soon as the scraper bar moves over the press bed.
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