How did I miss this thread, eh? I am falling down on the job...
The festival is at Carnival/Mardi Gras time, the prelenten time of year.
Best I've read about it is in a book on Venice and it's history by James Morris, I think it's called Venice, but I'll look up a link for you. Interesting book, held my attention...
James Morris is the literate travel writer who became, somewhere along the line, Jan Morris, a woman; I think she also wrote a book about that situation.
Anyway, I remember the book as one of my faves in my vast books-about-italy collection.
Found the link -
Venice, by James Morris