What do you think the problem was? We don't have the details.
What recipe did you use? There is no normal recipe. Did you let the mix sit after adding the water? I've never felt heat coming from the mix until it starts to cure.
How big was the smallest one, that you didn't unmold for 2 days? You can unmold most planters in 24 hours. Did you use a mold release or line your mold with plastic? How thick are the walls? Did you use peat moss? Do you sift your peat moss? Did you use horticulture grade vermiculite or perlite? There are so many variables. Got squirrels or other critters? I had a retriever grab one of my plastic bags and drag it away. The squirrels have jumped on my curing molds and knocked them over. Got kids? Got husband that moves things out of the shade to mow then forget to get them out of the sun and back into the shade? It could be something simple, like using a mold without enough support. Anyone else have some thoughts? Hope you figure this out. Billie

How thick were the containers? Two thin and if you were having difficulty removing from the mold, you may have cracked. If it was cracked or broken prior to removing from the mold the mix may be too dry. Agree with Billie - not enough details to figure out why.
Tell us what the mix was and how wet or dry the hypertufa was as us placed in the mold. How thick, and was the hypertufa moist the entire time it was in the mold, or did it dry out.

Mike

I think the problem was the hot water from the hose that had been laying in the sun all day. I didn't think about it until I went to mix and it was hot water. Pots were 1 1/2" or more thick. One was about 6"wide by 4"tall inside mold, 10" across by 3" tall inside mold, saucer like and other is probably 14" across by 7" deep outside mold. All were roundish so there were no corners that were thin. No mold release but a plastic bag liner. They came out of the mold fine. I left them in the mold because I just didn't get the time to take them out. It was top 80 degrees to low 90's so didn't think it would hurt to keep wrapped. I had misted them. I could of helped the smaller one crack when I moved it after unmolding. I just meant that I had used the same receipe that I had for many pots without a problem. Receipe was 1 portland, 1 & half vert. & 1 & half peat. Peat was sifted. Hort. grade vert. Mixture stuck together when I squeezed it with very little water. We have squirrels,cats and hubby but don't think it was them. The 3rd pot still doesn't have any cracks. I've sprayed it numerous times but no water bath. Kathy

LC - it is possible that the hot water had something to do with the cracking. Never saw it - but it is possible.
I would suggest that wheh you measure your ingedients that you use a small container - like a coffe can. 1 can - portland, 1 can peat, 1 can perlite and then 1 can water.
Putting the water in the can will allow you to make sure of two things - one that it is not too hot and two that you do not use too much water. Now the it is possible that you will use more or less than the 1 can of water but by measuring the water you are paying attention to how much water that you use.
-

Mike