the same thing happened to me when i did my first bowl. one thing i did wrong was making the walls too thin. i also think i didn't add enough water.

too much or too little water can be a problem
My rule of thumb - MEASURE ingredients - including water
I use equal part water , peat, perlite , portland.
Add water slowly ( you may not need all the water - depending on the temp outside, assuming you are making it outside!)
Once mixed --- squeeze a ball of tufa in your hands - a few drops of water should come out.

Also try a differnt mold - you are asking for problems trying to squeeze the mix into a 10" container. Try a larger bowl and apply mix to outside of bowl.
Also do not forget to use PAM spray on the mold to release the tufa from the mold the next day.

I made many mistakes until I got it the waty I like -

Mike

mamcc, The more details you give would help. What recipe did you use? How thick were the walls? Did you bang or flex the mold? Did you tamp the mix? Was it too cold? Did you add dye? Details please!?? Billie

Also, remember to give it enough time to cure. A good rule of thumb is 48 hours later. The more you wait, the more solid it will be. For larger projects, I'll wait as much as a week

amaretto, 48 hours is way to long for a 10" pot. 24 hours is usually long enough. Many of us wire brush or scrub or carve the outside and it would be too hard in 48 hours for hand tools. Billie