top | item 26555153

Letterlocking

168 points| krisbolton | 5 years ago |en.wikipedia.org

21 comments

order

gen220|5 years ago

There was a cool article on this subject a few weeks ago: https://www.npr.org/2021/03/02/972607811/reading-a-letter-th...

Basically, opening centuries-old letters that are sealed with this technique is usually a destructive process: you might end up rendering some portions of the letter unreadable.

As such, many of these letters have never been opened! They might contain interesting things, but we have no idea.

Some researchers figured out a way to "unfold" X-rays of these intricately-locked letters, to render the letter legible without having to actually open it! It's a pretty cool technique.

The underlying paper is here: https://www.nature.com/articles/s41467-021-21326-w

hinkley|5 years ago

Some of the things we've done with old letters are fascinating.

I remember when they figured out how to use spectral analysis to 'see' the solvents that soak into paper from the ink, allowing them to read words that had flaked off due to the ink or the paper delaminating, especially at the edges of paper.

msp-m|5 years ago

this is one of those technologies - drop a letter from centuries ago onto an x-ray and let it get displayed on a computer screen - that will really make future tech look like "magic"

SamBam|5 years ago

In the example image, it seems sealing wax is required to authenticate that the lock has not been opened.

If sealing wax is going to be used anyway, why not just fold the letter and seal with wax like normal?

signaturefish|5 years ago

It's pretty easy to non-destructively lift a wax seal off of paper, with a sharp, hot knife and a bit of practice. You can then read the letter and reseal it with a touch more hot wax or the back of a heated spoon (to melt the back of the original seal).

Not that I've ever done that, as a courier, in a live-roleplay game, ever. Repeatedly ;D

Depending on the security level of the letter, of course, a non-letterlocked letter might be pretty readable even if sealed. A simple letter where the seal authenticates the sender but doesn't protect the contents might simply be folded in three and sealed closed - you can bend and flex such a letter without breaking the seal to read most of it. A more important letter being _protected_ by a seal might be folded into an ersatz envelope and then sealed on the join ... but that's most of the way to a basic letterlock.

So, like all communications there's a tradeoff between complexity and security, and whether you're using the seal merely to authenticate the sender (which was pretty common) or also to protect the contents.

function_seven|5 years ago

With just a flat wax seal, is it possible to lift it off one surface, read the letter, then with a little extra wax, reseal the letter?

If there are other pieces of paper held in the wax like a 3D matrix of sorts, it gets much more difficult to undo then redo the seal.

bb123|5 years ago

Ah yes the original version of “warranty void if opened”.

akeck|5 years ago

There's a sub-culture of origami related to this called "Envelope and Letter Folding".

anorakoverflow|5 years ago

Looking at the links in the Wikipedia article I discovered this wonderfully “old web”-style page with various envelope folding guides[1]. I found it so endearing that I sat down and tried a few of them out, which was great fun.

[1] http://www.orihouse.com/elfa.html

Animats|5 years ago

There was at one time a stapler-like device which did that automatically. It cut a slot and a tab, and pushed the tab through the slot.

cbcrenshaw|5 years ago

I don't know much about the device you describe, but fastening papers with something like this is probably way better than staples if the goal is long-term storage. Staples and other metal fasteners are pretty destructive. The National Archives offers guidance for fastened document preservation, for example, here: https://www.archives.gov/preservation/holdings-maintenance/f.... Staples can add a lot of unneeded bulk to records, too.

dhosek|5 years ago

There still is. We have a couple of these in my house. It's not as effective as a metal stapler, but it works well enough for things that we don't need permanently connected (plus it's much safer for my 6-year-old kids to use).

codazoda|5 years ago

Apparently these are called a "paper clinch".

prionassembly|5 years ago

Something like this is mentioned in the Hagakure, but I didn't understand what it was for until now.