Electrotyping
Electrotyping is a chemical method for forming metal parts that exactly reproduce a model. The method was invented by a Prussian engineer Moritz von Jacobi in Russia in 1838, and was immediately adopted for applications in printing and several other fields. As described in an 1890 treatise, electrotyping produces "an exact facsimile of any object having an irregular surface, whether it be an engraved steel- or copper-plate, a wood-cut, or a form of set-up type, to be used for printing; or a medal, medallion, statue, bust, or even a natural object, for art purposes."
In art, several important "bronze" sculptures created in the 19th century are actually electrotyped copper, and not bronze at all; sculptures were executed using electrotyping at least into the 1930s. In printing, electrotyping had become a standard method for producing plates for letterpress printing by the late 1800s. It complemented the older technology of stereotyping, which involved metal casting. By 1901, stereotypers and electrotypers in several countries had formed labor unions around these crafts. The unions persisted into the 1970s, but by the late 20th century, after more than a century in widespread use for preparing plates, the two technologies had been bypassed by the transitions to offset printing and to new techniques for the preparation of printing plates.
Technical description
As with metal casting and stereotyping, a mold is first formed from the model. Since electrotyping involves wet chemical processes and is done near room temperature, the molding material can be soft. Materials such as wax, gutta-percha, and ultimately ozokerite were used. The mold's surface is made electrically conducting by coating it very thinly with fine graphite powder or paint. A wire is attached to the conducting surface, and the mold is suspended in an electrolyte solution.Electrotyping is activated by electric currents that flow between anode wires that are also immersed in the solution and the wire connected to the coated mold. For copper electrotyping, a typical aqueous electrolyte contains copper sulfate and sulfuric acid, and the anode is also copper; the arrangement is illustrated in the figure. The electric current causes copper atoms to dissolve from the anode's surface and to enter the electrolyte as copper ions. Copper ions are taken up by the mold's conducting surface at the same rate at which copper dissolves from the anode, thus completing the electrical circuit. When the copper layer on the mold grows to the desired thickness, the electric current is stopped. The mold and its attached electrotype are removed from the solution, and the electrotype and the mold are separated. An animation of the electrotyping process was produced in 2011 by the Metropolitan Museum of Art. Other metals besides copper can be electrotyped; similar procedures apply, but each different metal needs its own anode and electrolyte chemicals.
There is a second type of electrotyping that has been used in which the copper film is deposited onto the outside of a form, and is not separated from it. In this use the form is typically waterproofed plaster, which remains as a core after electrotyping. In German this method is known as Kerngalvanoplastik; the more usual technique described in the previous paragraph is known as Hohlgalvanoplastik.
Electrotyping is related to electroplating, which permanently adds a thin metallic overlayer to a metallic object instead of creating a freestanding metal part. Electrotyping and electroforming both produce metal parts, but differ in technical details. Electroforming involves the production of a metallic part around a metallic mandrel, although the term is sometimes used more broadly to encompass all electrodeposition processes. As noted above, electrotyping forms the part using a non-conducting mold or form whose surface has been made conducting by applying a thin coating of graphite or metal powder.
Invention and subsequent developments
At present, most sources credit Moritz Hermann Jacobi with the invention of "galvanoplasty" or electrotyping in 1838; Jacobi was a Prussian scientist who was working in St. Petersburg, Russia. Nineteenth-century accounts often credited Thomas Spencer or C. J. Jordan with the invention in England, or Joseph Alexander Adams in the United States; Heinrich in particular gave a thorough account of the controversies surrounding the crediting of the invention, along with a short biography of Jacobi, in an article honoring the centennial of electrotyping in 1938.The electrotyping industry was limited for some decades by the sources of the electric currents needed to activate the deposition of metal films into the mold; the rate of film growth is proportional to the magnitude of this current. In the initial work, the Daniell cell was used to provide these currents. The Daniell cell was largely replaced by the Smee cell after the latter's invention by Alfred Smee in 1840. Both of these cells are forerunners of contemporary electrical batteries. By the 1870s, mechanical generators were being used; the larger currents that could be sustained by generators enabled substantial increases in the rate of metal deposition during electrotyping.
Electrotyping in printing
One of the first applications of electrotyping was in printing. Initially, electrotyping was used to make copper reproductions of engraved metal plates or wooden carvings, which were used to print artwork. The electrotypes could be incorporated along with movable type to compose the formes for printing. Jacobi published his first account of electrotyping in October 1838. In 1839, electrotyping was used by Russian printers for government documents; the Russian Czar Nicholas I had immediately become an enthusiastic supporter and patron of the technology. In England, the first use of electrotyping for printing appeared in the London Journal of April 1840, and other English examples are known from later in that year. The image to the right shows one of the earliest uses of electrotyping in the United States; it is a comparison done by Joseph Alexander Adams in 1841 of the printed image prepared directly from a wood carving and of the image printed from a copper electrotype copy. Electrotyped copper plates could be formed into cylinders, which was valuable for use in magazine and newspaper printing.Electrotyping was also used to produce entire printing plates directly from the formes composed from movable type and illustrations. In this application, electrotyping was a higher quality but more costly alternative to stereotyping, which involved casting of type metal into a mold prepared from the forme. Stereotyping had been invented around 1725, and was already well-established when electrotyping was invented in 1838. Both methods yielded plates that could be preserved in case of future needs, for example in the printing of novels and other books of unpredictable popularity. The movable type used to compose the original forme could then be re-used. Both methods could be used to prepared curved plates for rotary presses, which were used for the longest print runs. The widespread adoption of electrotyping for this use occurred after mechanical electrical generators became commonly available around 1872. These generators supplanted the whole rooms of chemical batteries that were previously used to provide electricity for electrotyping. Batteries did not have the electrical capacity needed to rapidly deposit the electrotype. The advent of plating dynamos sped up electrotyping twenty times or more, so that an electrotype printing plate could be deposited in less than two hours. In addition, the chemical batteries gave off toxic fumes that had required their isolation in separate rooms.
Electrotype was also used to manufacture matrices that could be used as moulds for individual pieces of metal type. This had several advantages over conventional punchcutting in hard steel: only soft metal was needed for carving the type master, which was also useful for large sizes of type, since it was hard to drive large punches into a matrix effectively. It cut the cost of decorative types that would not be used as often as body text typefaces. On the other hand, it gave no steel punch that could be used to create multiple matrices quickly, and was reported not always to give such good results as steel punchcutting.
Electrotyping was used for general-purpose type manufacture in the nineteenth century, but was a somewhat disreputable process, leading to some typefounders disdaining it. This was because it could be used just as easily to pirate another company's type as for an original design.
By the 1900s printing plants often incorporated electrotyping and stereotyping departments, and electrotyping and stereotyping had become trades with associated apprenticeships. In the United Kingdom, the National Society of Electrotypers and Stereotypers formed in 1893, and continued to 1967 when it amalgamated with the National Graphic Association. In the US and Canada, the International Stereotypers and Electrotypers Union was formed in 1902; previously, electrotypers had belonged to the International Typographer's Union. In 1925 there were 6800 members, and in 1955 10,500. In 1973 the ISEU was absorbed into the International Printing and Graphic Communications Union. In 1978, an Occupational Outlook Handbook reported that 2000 electrotypers and stereotypers were employed in the US. However, job prospects were reported as poor. Offset printing has supplanted letterpress printing in most printing plants; the last letterpress facility for a newspaper was installed in the 1980s. For offset printing, the printing plates are typically prepared by coating them with light-sensitive materials, and creating the image on the plate by direct optical exposure ; stereotyping and electrotyping are not used.
A slight problem with electrotyping of type is that the new form is slightly smaller than the original, and this deviance could accumulate if a letterform was repeatedly regenerated. Stephenson Blake's solution was to squash type slightly in a press or file it down to broaden it before putting it into the electrotype bath.