Litho Printing - Its Modern Uses
Litho printing, also called lithography is a method of printing that uses a completely smooth surface, traditionally stone or a metal plate. Litho printing was invented in 1796, and it was initially developed as a method of producing theatrical works at low cost.
Modern litho printing involves creating an image in a polymer coating which is then applied to an aluminium plate. The surface of the plate is roughened and manipulated chemically so that some regions are hydrophilic and act to accept water, and repel ink, while others are hydrophobic and act to repel water and accept ink. As a consequence, printing can be done directly from the aluminium plate, resulting in a reversion of the image, or the image can be transferred onto a sheet of rubber.
The main process of litho printing is the production of hydrophobic and hydrophilic regions on the stone or aluminium plate. The terms hydrophobic and hydrophilic are chemical terms, literally meaning ‘water hating' and ‘water loving', respectively. Unlike processes of etching, or engraving, the plate does not act as a ‘stamp' with raised sections. Instead, the entire plate is at the same level, with the ink adhering or not based on chemical reactions.
In litho printing, once the plate is prepared it is introduced to a mixture of water and ink. This provides a double function. The ink binds to the hydrophobic sections, where it will be used in producing the image, while the water acts to wash the remaining, hydrophilic sections.
Generally, modern litho printing uses an aluminium plate as the medium, but sometimes limestone is also used. For this, the image is drawn directly on the plate with a hydrophobic medium, for example a wax crayon. There may be pigmentation applied to the media, so that the final drawing is visible. After this process, the stone is exposed to a solution of weakly acidified gum arabic which is applied to the stone. This results in hydrophilic gum arabic and Ca(NO3)2 being present on all surfaces that were not part of the image. This rejects ink, and can then be removed following the adherence of ink to the desired image.
Printing using litho printing is common where large volumes of printing are required. Offset lithography is one variation of litho printing, and is the most common type of printing available. This produces large volumes of text at low costs. In fact, almost any item that contains print and graphics that is mass produced is produced using offset lithography.
The most modern applications of litho printing now take advantages of photographic processes, with the plate being a photographic negative of the final desired image. The plate is roughened and covered with a photosensitive media, following which it is exposed to UV light. Despite its invention as far back as 1796, litho printing is the most widely used means of printing on mass.
Modern litho printing involves creating an image in a polymer coating which is then applied to an aluminium plate. The surface of the plate is roughened and manipulated chemically so that some regions are hydrophilic and act to accept water, and repel ink, while others are hydrophobic and act to repel water and accept ink. As a consequence, printing can be done directly from the aluminium plate, resulting in a reversion of the image, or the image can be transferred onto a sheet of rubber.
The main process of litho printing is the production of hydrophobic and hydrophilic regions on the stone or aluminium plate. The terms hydrophobic and hydrophilic are chemical terms, literally meaning ‘water hating' and ‘water loving', respectively. Unlike processes of etching, or engraving, the plate does not act as a ‘stamp' with raised sections. Instead, the entire plate is at the same level, with the ink adhering or not based on chemical reactions.
In litho printing, once the plate is prepared it is introduced to a mixture of water and ink. This provides a double function. The ink binds to the hydrophobic sections, where it will be used in producing the image, while the water acts to wash the remaining, hydrophilic sections.
Generally, modern litho printing uses an aluminium plate as the medium, but sometimes limestone is also used. For this, the image is drawn directly on the plate with a hydrophobic medium, for example a wax crayon. There may be pigmentation applied to the media, so that the final drawing is visible. After this process, the stone is exposed to a solution of weakly acidified gum arabic which is applied to the stone. This results in hydrophilic gum arabic and Ca(NO3)2 being present on all surfaces that were not part of the image. This rejects ink, and can then be removed following the adherence of ink to the desired image.
Printing using litho printing is common where large volumes of printing are required. Offset lithography is one variation of litho printing, and is the most common type of printing available. This produces large volumes of text at low costs. In fact, almost any item that contains print and graphics that is mass produced is produced using offset lithography.
The most modern applications of litho printing now take advantages of photographic processes, with the plate being a photographic negative of the final desired image. The plate is roughened and covered with a photosensitive media, following which it is exposed to UV light. Despite its invention as far back as 1796, litho printing is the most widely used means of printing on mass.
