Importance Of Lithographic Platemaking In Offset Printers
The fact that web offset lithography is the most common techniques for high speed printing where large rolls of paper are consumed with in-line finishing systems and printing units. Although, they do not come cheap and are bulky but are widely used for applications having larger volumes notably printing newspapers and magazines.
Web offset lithography contains different units all having their proper channel of operation and performs their required job in a specified way. Platemaking is also a separate unit and important part of the process which is almost the same in both techniques weather the printing is carried out on sheet-fed or web-fed techniques.
Lithographic Platemaking Process:
In a general way, the platemaking process ensures that all of the image areas in a plate must be lipophilic and hydrophobic. Lipophilic and hydrophobic means that the image portions of the plates must be repellent to water and alternatively receptive to oil mainly ink.
Offset printers in Dubai also have other chemical principles for the non-image portion of the plate. They are lipophobic meaning that they are repellent to oil and hydrophilic or receptive to water. Both of these chemical properties possessed by the image and non-image portions of the plates ensure the ink adhere to the plate’s image area only.
Desensitization Process:
Over the course of overall press-run process, the plate remains desensitized by the continuous addition of gum through desensitization process. The water-receptive coating continuous increase and addition is too important on the non-image areas of the plate for effective result of printing. Gum Arabic is extensively used and an idle solution for water-receptive coating solution of this process.
Plates Inspection:
The plates are occasionally inspected and observed for minor corrections, scratches and other defects before mounting. Those unwanted specks and undesirable image areas that are not required to be printed are erased before treating the plate with gum. All the empty places in solid image areas are filled while scratching them before applying ink to avoid undesirable results. However, such manipulation must be performed for the most minor defects only.
Recommendations Of Press Manufacturers:
Press manufacturers have determined printed image’s position on the paper and alignment of the image which are followed in the mounting process of plate. They can be repositioned for keeping the image on centre of the page.
The recommendations also include guidelines for proper formulation of fountain solution to prevent continual plate maintenance. Also they include prevention from extended shutdowns of the press when plates are still inked because blinding might initiate on the image portions of the plate when because of gum that dries on it.
Scumming and Blinding:
Printers in Dubai that belong to press solution providers using the machines for large-volume applications continuously are observing two common defects in the plates. Scumming and blinding are respectively the non-image portion’s ink receptivity and image areas ink-repellence qualities respectively. The main cause of these defects is improper fountain solution formulation during damping.