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Hangeul sign-engraving machine

Last summer I was privileged to visit the glorious Letterpress Museum in Paju Book City, where I spent several hours and took a collection of photos that are probably not of interest to anyone but letterpress geeks, and perhaps not even to them.

Looking back at the photos it's not always clear to me why I took each one. But some of them I can remember. For example, this one:

This is not exactly letterpress. It is a device for engraving lettered signs on thin strips of metal or perhaps plastic. Happily I don't have to spend too much time explaining this because Marcin Wichary has just published an extensively-illustrated article about the Latin-script version. The only thing different about this one is the fonts, which are for writing Korean in Hangeul script rather than English in Latin script.

(Here's my real-quick summary. There is no ink. A stylus goes into the grooves of those brass templates. The stylus is attached with a pantograph to a router bit that rests on the object that the operator wants to engrave. When operator moves the stylus in the template grooves, the router bit follows their motions and engraves matching grooves in the target object. By adjusting the pantograph, one can engrave letters that are larger or smaller than the templates.)

Hangeul has an alphabet of 24 letters, but there's a difficulty in adapting this engraving technique for written Hangeul: The letters aren't written in a simple horizontal row as European languages are. Instead, they are grouped into syllables of two or three letters. For example, consider the consider the Korean word “문어”, pronounced (roughly) "moon-aw". which means “octopus”. This is made up of five letters ㅁㅜㄴㅇㅓ, but as you see they are arranged in two syllables 문 ("moon") and 어 ("aw"). So instead of twenty-four kinds of templates, one for each letter, the Korean set needs one for every possible syllable, and there are thousands of possible syllables.

Unicode gets around this by… sorry, Unicode doesn't get around it, they just allocate eleven thousand codepoints, one for each possible syllable. But for this engraving device, it would be prohibitively expensive to make eleven thousand little templates, then another eleven thousand spares, and impractical to sort and manage them in the shop. Instead there is a clever solution.

Take a look at just one of these templates:

This is not a Hangeul syllable.

Rather, it is five. The upper-right letter in the syllable is the vowel, and the template allows the operator to engrave any of the five vowels

ㅣㅓㅏㅕㅑ

to produce the syllables

잉 엉 앙 영 양

pronounced respectively "ing", "ông", "ang", "yông", and "yang".

Similarly this one can produce six different syllables:

The upper-left part can be used to engrave either of the consonants ㅅ or ㅈ and the upper-right part can be used to engrave any of the vowels ㅣㅓㅏ, to produce the combined set 싱 성 상 징 정 장. I'm not sure why this template doesn't also enable vowels ㅕㅑ as the other one did.

In the picture at top you can see that while the third template can be used to engrave any of the three syllables 송 승 숭 the operator has acutally used it to engrave the first of these.

This ingenious mechanism cuts down the required number of templates by perhaps a factor of five, from ten boxes to two.

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