Bad Casting

The last batch of castings just wouldn't harden. Now I'm trying a more viscous slip, and waiting longer to drain the molds. Trial and error, with an emphasis on error. The references I have detail casting smaller pieces with a white clay, so I need to learn how do it under my parameters.
******************************************************************************************After 17 hours in the molds, all the castings have released perfectly. It's weird, that it takes so long, but the finished product is very nice. I hope I'm good enough where I can replicate this latest process every time, and later learn some tricks, over time, to do it faster.