A flourish is a decorative touch that breathes life into words. It energises a page and makes your letters truly unique. Linda Hutchinson – 3rd Manual for the Calligraphic Arts
A flourish is the ornamental embellishment of a letter or letters. Diana Hardy Wilson – Encyclopedia of Calligraphy Techniques
Flourishing can be attached to letters to on ascenders, descenders, double letters, end of words and capitals.
Flourishes should not be tight (like a spring) and have a nice lot of space in their counter shapes. They should not obscure or 'bash into' other letters.
Practise / warming up is important before executing a flourish so that it looks as though it belongs. It becomes part of a letter and not an 'add on'. They should flow freely and be incorporated into the whole design. Strokes supporting a flourish should keep their integrity within the x height margins.
I noticed that some of the basic principles of lettering need to be revised. Will leave that until another time but it has to do with the shape of the mother letter, O. Both copperplate and italic are cursive scripts which makes this shape all the more important.