When I was a child, when a lot of guests gathered, I loved to add a small drop of iodine to the tea.
The color and taste of the tea from this does not change, but if you soak the bulk in it, it is painted in a perforating blue color.

Children at the adult table pay little attention.

This is how you sit, make a bite, bite, chew off gradually all the conversations go away, no one eats or talks anymore - they look at everything with horror...