Well, I tried some banknotes with mixed results and a few lessons. I tried a couple of really dirty folded notes, the worst in Gilbert's (my son's) collection and one newer one that had some heavy creases. These were the ones I used:
I also did a Chinese note in similar condition but forgot to take a before shot. The newer note was from Singapore and this one showed that I was not thinking clearly, but more of that later. I gave the notes a good wash in hot water with a couple of drops of dishwashing liquid. I used a camel hair brush for this, the one I use for washing old hinges off of stamps.
As before, I gave them three, one minute bursts in the microwave, allowing them to cool in between each burst.
I found that where a note has been carried folded in a wallet for some time, the damage is too great to repair and the line is still visible. Even so, the condition of these is improved a little.
Here is the Chinese note which also looked like it had been in a wallet for years.
As for the Singapore dollar, well that's another story. While it was microwaving I became aware of an ominous smell. The lesson I learned was this:
Never microwave a note with a metal strip in it. It cost me not only the note (well it cost Gilbert the note), it ruined the pads in the press. Ah, well! I like to learn new things. I can't help thinking I should have realised this would happen though.