Look at the hypertyfa forum..I am sure they have used those things for molds. Even on garden junk they have been used in the past. I didn't do anything with tufa or concrete so I can't give you an answer.

hi rhonda
they work great and almost any oil works as a release. Pam is good. Vegi cooking oil works well.
I suggest you drill small holes in the molds to reduce the suction and make them easier to remove. All the release film in the world won't help release the vacuum created between the damp tufa and your mold.

Thanks for the suggestions. Fauxstoner, I filled a vintage jello mold last week I think it's going to make a great boat anchor(ha!)cause I can't get it out of the mold so I appreciate it.

I like plastic best. Metal sometimes reacts to the cement and you do not get a smooth surface. The palstic dries out after several uses so if you are making say a border, metal would be needed. I love trays from the party store. Lots of fun shapes. I use JELLO pans that come in the baking isle. I use crisco for the oil. it is cheapest.

Thanks. I just read on another site that if you paint the interior of the metal pans with primer used on cars in autobody shops you have much better luck with the metal pans. I've found most of my pans at the Goodwill or other thrift shops so I don't have alot of money invested. I bought a silicone bundt pan the other day at Walmart. I'm anxious to see how it turns out.

Wilton cake pans work great too. I find them at garage sales.

What fun! I've made Jello molds for years. I used Vasaline to grease the molds, then poured the cement. I found out the hard way they split in half in about a year so I would suggest the fibers used in cement. Can't remember the name but Home Depot or the like will know. I used the longest deck screws I could find to hold two together. It helps if you have two molds the same, if not finish one with the screws sticking out and pour another and when it sets up flip it over onto the finished one then back over and let it harden. I was real fond of the train cake pans and the flower molds. Also used molds with holes in the center and sliped the finished double sided molds down lengths of pipe like a totem pole.

Thanks for suggesting the fibers. I am wanting to sell them on consignment so I definitely don't want them to split!!
You can use the molds with the centers in them as a stand for a gazing globe.