I also slice paper thin on a mandolin. On a steep angle. If not even as a ribbon.
Served right away they are crunchy. Wait an hour they are noticibly softer. Over night they get very soft.
I will thinly slice red onion in with them... or maybe radishes. Both on the mandolin.
(Although I've been told by friends and my kids to stop as my fingers are getting too short and will not
grow back - sniff, 'cause they tell me I'm not a 'real' dragon
My mother would just soak regular slices in plain white vinegar - not sure if she added a tiny touch of sugar or not.