In printing, a stereotype, stereoplate or simply a stereo, is a solid plate of type metal, cast from a papier-mâché or plaster mould taken from the surface of a forme of type. The mould was known as a flong.
Background
In the days of set movable type, printing involved placing individual letters (called type) plus other elements (including leading and furniture) into a block called a chase. Cumulatively, this full setup for printing a single page was called a forme. Ink was then applied to the forme, pressed against paper and a printed page was made. This process of creating formes was labour-intensive, costly and prevented printers from using their type, leading, furniture and chases for other work. Furthermore, printers who underestimated demand would be forced to reset the type for subsequent print runs.
... while Nathaniel Hawthorne's publishers assumed that The Scarlet Letter (1850) would do well, printing an uncharacteristically large edition of 2,500 copies, popular demand for Hawthorne's controversial "Custom House" introduction outstripped supply, prompting Ticknor & Fields to reset the type and to reprint another 2,500 copies within two months of the first publication. Still unaware that they had an incipient classic on their hands, Ticknor & Fields neglected at this time to invest in stereotype plates, and thus were forced to pay to reset the type for a third time just four months later when they finally stereotyped the book.
While stereotypes were useful in book publishing, it was in newspaper publishing that they came into their own. Books were normally printed not as single pages, but as set of multiple pages at a time. Thus a single volume 320 page book needed 40 stereos for an eight-page imposition, or twenty stereos for a 16-page imposition. This contrasts with newspapers, where a Sunday edition of a major newspaper could require as many as 6,000 stereos.
Advantages of stereotypes
Stereotype offered the following advantages:
They allowed the printer to quickly distribute expensive type, thus reducing the amount of type the printer needed to keep. In some cases, contracts with publishers required printers to keep type set up for anything up to six months in case further editions were needed. Facilitated the distribution of the set-up type, as stereos were far lighter and less fragile than formes full of type. This was particularly important for syndicated news services. Facilitated the storage of set-up type. Stereos were far lighter and took up a lot less space than formes full of type. This meant that the printer did not have to set up the work again. Stereo plates could be stored for several decades. A large number of such stored stereotypes were melted down in 1916 in the UK in support of the war effort. In 1910 for example, Hodder and Stoughton published G. A. Henty's Friends though Divided: A tale of the Civil War printing the book, apart from the preliminary pages, from the stereotypes used for the initial 1883 edition by Griffith and Farran. The same stereos were used for reprinting in 1917 and in the 1920s. When they sold a copyright to another publisher, publishers often sold the stereotypes as well. Enabled the printer to quickly set up the same text multiple times so that he could print a given text, e.g. for a handbill, several times on the same sheet of paper and then separate them. This was faster and cheaper than doing them individually. Enabled the same text to be printed on multiple presses at the same time. Dalgin gives the example of one instance where thirty stereos were produced from a single flong for this purpose and states that there is no reason why more could not have been cast.
Invention
English sources often describe the process as having been invented in 1725 by William Ged, who apparently stereotyped plates for the Bible at Cambridge University before abandoning the business. However, Count Canstein had been publishing stereotyped Bibles in Germany since 1712 and an earlier form of stereotyping from flong was described in Germany in 1702. It is even possible that the process was used as early as the fifteenth century by Johannes Gutenberg or his heirs for the Mainz Catholicon. Wide application of the technique, with improvements, is attributed to Charles Stanhope in the early 1800s. Printing plates for the Bible were stereotyped in the US in 1814.
Moulding materials
The following have been used for moulding type to create stereos: