How long from caterpillar in J to chrysalis?

This is my first year raising Monarch Butterflies. I would like to know how long it takes the caterpillar to Chrysalis after it attaches itself into a J. Mine has been in that state for about 8 hours. I keep checking to see if it has become a Chrysalis but it is still hanging in the J position.
thank you for your help.

Karen says:
It can vary, but usually within 12 hours or so the caterpillar's skin splits and reveals the beautiful chrysalis underneath! I hope you can observe this miraculous event!