I asked an AI about this: my question, and the answer is shown below. I asked a follow-up about evidence that the Royal Family used any of these methods: the answer was, essentially, there is no evidence.
The hectograph looks to be the most likely: “slower and more cumbersome” sounds very British.
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In 1918 was there a method by which duplicates of a handwritten letter could be produced (not carbon paper).Yes, in 1918 there were several established methods-other than carbon paper-for producing duplicates of handwritten letters.
## Letter Copying Press
One widely used method was the *letter copying press*. This device allowed for the duplication of handwritten letters by transferring ink from the original onto a thin, dampened sheet of tissue paper. The process involved:
- Writing the original letter with special copying ink that remained wet for a period.
- Placing the original face-down onto a moistened tissue sheet.
- Pressing both together in the copying press, causing some of the ink to be absorbed by the tissue, thus creating a legible reverse copy[1][10][14].
This method was common in offices and for personal correspondence from the late 18th century through the early 20th century, and was still in use in 1918.
## Hectograph
Another method available by 1918 was the *hectograph* (or gelatin duplicator). This process involved:
- Creating a master copy using special aniline dye-based ink.
- Pressing this master onto a gelatin surface, which absorbed the ink.
- Laying blank sheets on the gelatin to transfer the ink, producing up to about 50 copies per master[1][6].
The hectograph was slower and more cumbersome than the copying press, but it allowed for the duplication of handwritten or drawn originals.
## Polygraph
The *polygraph* was a mechanical device that allowed a writer to produce a duplicate in real-time. It used a system of linked pens so that as the writer wrote the original letter, a second pen created an exact copy on another sheet. While the polygraph was invented in the early 19th century and used by notable figures like Thomas Jefferson, it was never widely adopted due to its mechanical complexity and maintenance issues[1].
## Stencil Duplicators (Mimeograph and Papyrograph)
Stencil duplicators, such as the *mimeograph* and *papyrograph*, were also in use by 1918. These methods typically involved:
- Creating a stencil by writing or tracing with a stylus or special ink that cut or burned holes in a waxed or varnished sheet.
- Placing the stencil on a duplicating machine and forcing ink through the holes onto blank sheets below[1][2].
While these were more commonly used for typewritten or printed documents, handwritten stencils were possible, especially for short runs.
**Conclusion:**
In 1918, besides carbon paper, the most practical and widely used methods for duplicating handwritten letters were the letter copying press and the hectograph. Both allowed for the reproduction of handwritten originals, with the copying press being particularly common in offices and for personal correspondence[1][10][14].
Sources
[1] Duplicating machines - Wikipedia
https://en.wikipedia.org/wiki/Duplicating_machines[2] Mimeograph - Wikipedia
https://en.wikipedia.org/wiki/Mimeograph[3] How to Write Letters: A 19th-Century Guide to the Lost Art of ...
https://www.themarginalian.org/2012/12/21/how-to-write-letters-1876/[4] Letterlocking a Jane Austen Letter
https://janeaustensworld.com/2023/10/17/letterlocking-a-jane-austen-letter/[5] early copying methods Archives - Mimeograph Revival
https://www.mimeographrevival.com/posts/tag/early-copying-methods/[6] [PDF] A survey of the material deterioration of office copies - Metamorfoze
https://www.metamorfoze.nl/sites/default/files/documents/OfficeCopyingResearch.pdf[7] Manuscripts | Information Services - Queen's University Belfast
https://www.qub.ac.uk/directorates/InformationServices/TheLibrary/SpecialCollections/Manuscripts/[8] Carbon copies for duplicating documents in the past - 1900s.org
https://www.1900s.org.uk/carbon-paper-duplication.htm[9] [PDF] [pre-print] An authorship analysis of the Jack the Ripper letters
https://research.manchester.ac.uk/files/63686674/pre_print_An_authorship_analysis_of_the_Jack_the_Ripper_letters.pdf[10] Conservation: Mann's letter copying books - Hagley Museum & Library
https://www.hagley.org/librarynews/conservation-mann%E2%80%99s-letter-copying-books[11] Origins and history of Bridge
https://www.ebu.co.uk/origins-and-history-bridge[12] Use of the typewriter on the western front - Page 2 - Great War Forum
https://www.greatwarforum.org/topic/258384-use-of-the-typewriter-on-the-western-front/page/2/[13] The lost art of reading other people's handwriting - BBC News
https://www.bbc.co.uk/news/magazine-36168408[14] Letter copying press | Canada Science and Technology Museum
https://ingeniumcanada.org/scitech/artifact/letter-copying-press[15] Calligraphy - Writing manuals and copybooks (16th to 18th century)
https://www.britannica.com/art/calligraphy/Writing-manuals-and-copybooks-16th-to-18th-century