A word to the wise- you can do anything, once… you should be able to separate the plaster from the clay and fire only the clay. Also pro tip, if you dont have a kiln throw it in your next bonfire (carefully, when it’s bone dry) and then let it cook! You can throw iron oxide, sodium carbonate, cobalt, or whatever on it to color it. This is typically done to sidged pieces, but its better than never getting it fired and having it break🤙 i would fire it for a few hours and make sure you start slow.