it was near the end of her presentation, when she was taking us through the process of firing the pottery after it had been carefully kneaded, spun, and shaped into the exact piece that the potter had planned. after it's molded, it has to be thrown into a kiln at 1800 degrees to be "fired". if it doesn't go through the fire, it can never be used. it will just crack or melt back into a messy lump of clay.
after the fire, it is thrown into a trashcan with newspaper and everything goes up in flames again. when that's finished and the lid is removed from the trashcan, can you guess what's there? well, yes, a dirty piece of pottery that needs some polishing up, but also... ashes.
the pottery has to go through the fire before it can be used. but when the fire is over, the Potter reaches in carefully, and pulls the beauty from the ashes. He cleans and scrubs and polishes until this piece, that He created from a lump of clay and for which he has planned a unique purpose, is ready to be filled up and used. filled up with Living Water... to be poured out into other pots.
When you pass through the waters,
I will be with you;
and when you pass through the rivers,
they will not sweep over you.
When you walk through the fire,
you will not be burned;
the flames will not set you ablaze.