DIY rock

[thrillreefer]

This thread has a ton of good information: https://www.reef2reef.com/threads/diy-rock-tutorial-info-thread-rocks-walls-floors-etc.31971/

This thread is gold!

 

[Roadkillstewie]

most plastic, silicone, latex and the like it won't adhere to.... you can make hard mold that..you clamp together, put a garbage bag inside and pour the mix into the bag.

aidditionaly, if you give it time to...soft set, then remove you can further shape/roughen etc with brushes, scrapers etc and then let cure.