The Lithographic Printing Process

What Is Litho Printing

History of Lithography

Applications of Litho Printing

The Lithographic Printing Process

 

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The term Lithography literally means writing on stone in Greek. Litho printing was discovered in 1798 by Alois Senefelder and has grown into a popular printing process with artists and commercially.

There are several steps involved in Senefelder’s original Litho printing process. These have been modified, adapted and innovated to become the offset lithographic printing so popular today, but some arxtists feel that Senefelder’s method allows for very high creative expression. The process adds individual character to every creation that can never be replicated.

Graining

The first step in the litho printing process is graining. A limestone quarry North of Munich is the source for the world’s most superior litho stones. A litho stone must be grained after each use. A stainless steel disk called a levigator is used to grain the litho stone with a mixture of carborundum and water. The stone is then ground with finer grit leaving it smooth for the next drawing or painting. A new litho stone is generally about 10 cm thick and only 1 mm needs to be taken off for each new drawing. So a litho stone can last for a few years if kept with care.

The Artwork

Once the stone has been grained and is ready for the image, the artist must choose the image he wishes to create. The first step is to draw a barebones outline of the final image on tracing paper. Since the artwork on the stone will have to be drawn in the reverse, tracing an outline helps.

The finished line drawing is traced onto the stone using a sheet smeared with iron oxide powder to act as carbon paper. The iron oxide will leave a red outline of the image that can act as a guideline for the artist. The artist can then start drawing on the stone and filling in all the details using oil based ink or a litho pencil. In fact anything oily will leave an imprint on the stone and can ruin the image so the artist must be extremely careful when making the artwork. Sandpaper can be used to sharpen the litho pencil if fine lines need to be drawn.

If the image is to be multi colored then the process becomes far more complicated. Each color will require a separate drawing on the stone. For all the drawings to align correctly, it is vital to make registration marks. A simple black and white litho painting that requires just one run can take up to 40 hours of hard work to create.

The Chemical Processing

This is by far the trickiest part of litho printing. It is also the basic fundamental on which litho printing works: oil and water do not mix.

Lithography uses just one surface area for the image and non-image areas. Hence the two are separated using a chemical process that involves an etch. An etch is a solution of gum Arabic and nitric acid.

The first step of processing is to apply rosen powder to the image area and wipe it off. Follow this with a coat of talcum powder. The image area is then buffed vigorously. Then the etch solution is applied using a brush over the entire surface. The stone accepts this solution while the oiled image area repels the solution. The etch is left for about five minutes and then buffed off the stone.

Then comes the toughest part. An oil-based solvent is poured over the stone and the entire image is washed off. A thin layer of oil-based ink is then wiped over the image area with a clean rag. The layer of water-soluble etch gum is then removed.

A leather roller is then rolled on an ink slab and rolled over the surface of the stone. The ink is rolled several times over the stone and the stone is sponged between each roll. The stone is then allowed to dry.

The entire process from rosen powder to rolling ink is repeated several times to make the image as stable as possible before printing.

The Printing Stage

The stone is inked with the ink color that the image is to be printed in. Then a sheet of paper is laid face down on the stone. A tympan or sheet of plexiglass is placed on the paper. The press bed is then moved horizontally to a point where the scraper bar is lowered onto the tympan. As the scraper bar moves over the press bed, the image is printed onto the paper. The paper is then removed.

The stone is immediately sponged wet and the inking process repeated for another print. To print 50 copies of the same drawing you would need at least 8-10 hours for each color assuming you don’t have any problems during the entire process.

Nobody ever said litho printing was a quick process!

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