Printing: Lithography, and Offset. What are they?

By Jason Wilson

January 25, 2021

 

Printing, as a practice is any process in which a single image is replicated. The history of this practice can be traced back to one degree or another for centuries. As a process it replaced the need to hand make each document, image, or piece of artwork one at a time.

Through many innovations the process has moved from rubbings of engravings, to pressing wood and metal engravings, to movable type (Thanks Johannes), to limestone plates, to metal plates, to the modern process of offset printing using a metal plate and a rubber blanket.

Around 1796 a Bavarian playwright named Alois Senefelder accidentally discovered that by writing his scripts with greasy crayon on slabs of limestone allowed him to reproduce them with rolled-on ink.  The local limestone he used retained the image so well that any crayon marks applied to its surface, even after repeated inking and printing, would lithograph (Latin for stone, litho, and mark, graph) and could be printed in almost unlimited quantities.

So why did it work?

Because by making the now prepared limestone wet any ink applied would stick only to the crayon and so only the image would transfer to the paper. Because oil and water don’t mix.

Yes, this means they had to put everything onto the limestone backward so it would print correctly.

More on that later.

Because of lithography’s ease of use and cost effectiveness it quickly found a large market for use. Soon it was being used in commerce, and was embraced by many of the artists of the time. Eventual improvements in technology allowed for the use of multiple colors and increasing the size of the printing base. Color lithography led to an increase in the production of artwork and book printing with color illustrations. A perfect example being Charles Dickens book “A Christmas Carol”. In its original edition, his classic story was filled with color lithographed illustrations but also produced at such a cost that it was affordable to the average consumer.

Advertising in the 1880’s and 1890’s was revolutionized by the production of large color mural posters.

In 1790 the first patent for a rotary printing press was issued to William Nicholson. His design would be improved upon over time and in 1844 Richard March Hoe patented the rotary drum press and dramatically increased the speed of printing. This became known as the “lightning” press.

In 1875, Robert Barclay of England developed the offset printing process for printing on tin. The rotary press used a metal cylinder wrapped in cardboard that transferred the ink to the flat metal printing surface.

In 1880 they found that a rubber blanket worked better than the cardboard and they began using the same process to carry paper instead of metal.

When photography became popular in the early 1900s, the once-flourishing lithography began to fall out of favor. Photoengraving began to be used instead.

In 1901 United States citizen, Ira Washington Rubel, while working on his press forgot to load a sheet during a printing, he found out that the rubber mat produced a much more accurate image than the metal.

So in 1903, the Potter Press Printing Company in New York created a printing press that employed Rubel’s new design. Having reworked the process to now have a positive image on the metal plate transfer the reversed image onto the rubber blanket that would now transfer the positive onto the paper, modern offset printing was born.

Though the plates and the machines that use them have advanced and innovated significantly since that time, this same technique is used today to provide the highest quality printing in the world.

Today, we can print directly on to the metal plates with a laser imaging system. This eliminates the need for harsh chemicals, the creation of film negatives and a number of other steps that were necessary only a few years ago.