The kids love the story of Saint Januarius (San Gennaro) and I was only too happy to tell it to them on Friday ahead of his Saturday feast. I typically use his Wikipedia page as a starting point, since it has some scientific information toward the bottom (that's the first thing they ask... it can't be a miracle so what's the scientific explanation?).
I saw this article in the NY Times about the liquefaction and plan to show it to the kids tomorrow as a follow-up.
The scene was familiar on the feast day of the patron saint of Naples, St. Januarius: the packed cathedral; the procession with the saint’s relics, including two glass vials said to contain his clotted blood; the mounting anticipation during the solemn ceremony, culminating in an explosion of applause at the archbishop’s joyful announcement: “I give you the good news, the blood has liquefied.”
...Little is known about St. Januarius, believed to have been a Neapolitan bishop and early Christian martyr, whose relics are preserved in an ornate chapel in the Naples Cathedral. The liquefaction of the substance that the faithful believe to be his blood takes place three times a year, in December, May and on Sept. 19, coinciding with his feast day. It was first recorded in 1389.
Theologically, the Vatican has never accepted the liquefaction as an official miracle, preferring to refer to it as an inexplicable phenomenon, said Gennaro Luongo, a professor of hagiography and ancient Christian literature at the University of Naples Federico II. But the Vatican acknowledges the widespread veneration of the saint.
“Since the 15th century, a popular belief holds that if the blood does not liquefy or only partially liquefies it bodes badly for the city,” Professor Luongo said. “People poke fun at this, but predictions are common to many religions. It is part of popular religiosity.”
Over the centuries, many have tried to find scientific explanations for the phenomenon, and Cardinal Sepe has said, according to Italian news reports, that he intends to have the liquid studied.
“I put myself at his disposal,” said Luigi Garlaschelli, a chemist who closely examined the liquid in a previous study concluding that thixotropy, the property of certain gels to liquefy when they are shaken, might be one reasonable explanation. But because the vials are sealed, he was doubtful that any future experiments would be carried out on the substance itself.
