sjmarq something that is not often mentioned is that wet tufa creates considerable vacuum between itself and your mold.
Yes you should have used a release medium, either something like heavy mineral oil, Pam, or my favorite plastic wrap, because it does help reduce sticking.
Avoid motor oils or WD40, both have chemicals in them not good for your skin or your lungs.
To avoid vacuum you can wait until the tufa has dried a little more this allows air to be drawn through it as you slowly pul on the bowl.
A firm gentle pull is the ticket, it can take quite a few seconds to break the suction.
The other simpler solution is to predrill a whole bunch of small airholes into you plastic mold.

I had that problem with a bowl I did. Really torqued me off, I worked and worked at it. Finally my girlfriend said why don't you soak it in hot water, I did and it popped right out. I even used a release in it. But yes always try to use some kind of release agent. It may be a failure but you have learned from it. Maybe some of the pieces can be salvaged for another project.
Paws

sjmarq,

I'm sorry you had a bad first experience. Was your mold hard plastic or flexible plastic. When I use flexible plastic I don't use any mold release and I've never had a problem getting projects out of the mold (I always use very smooth plastic). I wait until I can see the 'tufa' very slightly pulling away from the sides of the bowl, I flex the bowl out just a bit all the way around, then I just tip the bowl over gently onto my hand and it usually just slides right out. If it doesn't come out easily I wait a bit longer and then try again. The ridge may have been a problem. I do use pam on hard plastic molds as I have found the hard plastic is harder to remove the project from. I had a problem removing a project from the a hard plastic mold just the other day (I had forgotten the pam). I thought it was forever stuck together. Try as I might, that puppy wouldn't budge. My husband said, let me try to get it out. He turned it upside down and smacked it hard on the table while I held my breath (I just knew it would break). It popped right out and is just fine. I wouldn't recommend this method though.

Paws, Thanks for the hot water tip. I will have to try that if I have a problem again.

Amy

lololol sjmarq u did better then me !!!! on ur frist one i still cant get out . ill try to put some pic up .

can some one tell me how to put on pic. ? thanks katy