Metal finishing Q&As since 1989

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Perkins' Permanent Stereotype Steel Plate: can cast steel have been used successfully?

February 1, 2010

I am researching the above topic (for a book describing the chemistry and mechanics of printed dress fabrics 1760-1860), having a hard time finding out whether the following is correct. I think it must be, but can't be sure.

As far as I can tell, Jacob Perkins' invention of the 1790s consisted of dozens of small engraved steel dies interlocked, puzzle-like, precisely fitted inside a frameÜreferred to as a "matrix". This composed a banknote design intended to confound counterfeiters by its technical complexity and state-of-the-art engraving. For a number of reasons it seems crazy that this matrix would be used directly to print the paper notes.

The title of the invention seems to demand that the process include making a mold of the matrix from which a CAST STEEL printing plate- a stereotype- was derived, leaving the precious, pricey matrix in fine "permanent" condition for the next time it was needed. Right? But I have found no period writers who have indicated that was done. The patent office record has been lost in a fire. And I have been told that cast steel would be too brittle to be used for printing.

In the very early 19th century Perkins developed a successful, proprietary softening/hardening procedure Ü enabling, later, the production of a relief-patterned soft steel "roller die" by pressing it against the hardened matrix. This roller (subsequently hardened) was used in turn to 'engrave' a soft steel printing plate, subsequently hardened (or copper, if longevity was not important). (siderography, patent 1813).

When the process was adapted to take advantage of Spencer's geometric lathe around 1816, a soft steel plate was substituted for the multi-die matrix. It was engraved with the lathe, hardened, and from that point the procedure continued as described above. One 1867 writer indicates the use of a fine CAST steel plate for the initial flat die- why would he say that if a cast plate was so certain to break? I assume the answer is- it didn't matter as long as the hardening process did whatever it was designed to do.

In short, is it reasonable or not, to assert that there had to be a stereotype plate in the 1790s (to about 1804), even if that meant using cast steel, and is it reasonable that a "fine cast plate" would be specified for the die-plate in the c1816 process?

Thank you for reading this far!

Susan Greene
Independent scholar, author - Alfred Station, New York