Continuing on from yesterday…
Even if you use a cipher system that does not carry incriminating evidence, you’re still left with the problem of sending the message. There were more than a few German spies picked up by the British in WW2 because one of their suitcases concealed a radio set.
If a message is obviously secret, even if it can’t be read, it’s obvious that the sender was trying to hide something. That could mean a short stay in a nasty prison followed by a short drop on a patented neck stretching machine or a shave with the ‘national razor.’ Neither is recommended for your health.
By the way this is a problem with book codes. Possession of a certain edition of a book, unless it’s dead common, could be evidence.
So what is a refined genteel lady of the regency to do?
Secret inks and concealed communications.
Step 1: write a letter. Not a problem, then as now females wrote lots of communications. Not email, twitter or texting, but on paper. Remember to inquire after everyone’s health and to tell the recipient up front that everyone here is well. (or not).
Step 2: Prick out or underline certain letters or words in the message. These are the real message. If these markings are noticed, and they will be if they’re in plain ink, you may be in trouble. On the other hand, if they spell out a love missive, you will be excused. It was not uncommon in the days when parents read every young ladies correspondence, to use a subterfuge like this.
Step 3: Use a secret ink to mark out the real real message. You could skip step 2 if appropriate.
So what can you use for an ink?
Here’s the problem, possessing the ink is evidence of your intent to conceal. A Lady of Quality would have vinegars, a few cosmetics, and even the contents of the ‘gozunda’ available to her. These make reasonably decent ‘organic’ inks, where the compound alters the browning temperature of the paper. Heat it and the message is revealed. (There were ‘sympathetic’ inks which required a developing reagent available at the time, but they’d be problematic for a Lady to be carrying around.)