Fill the balloon with water . This image illustrates why you don't completely fill the balloon you should always leave some room in the neck of the balloon, then as the form dries the pressure has somewhere to go and your clay wont split like that.
this is soo cool. making imprints in clay and plaster casts Rachel Dein, Tactile Studio — The Nice Niche
20 cement and concrete DIy craft projects from Too Much Time on My Hands
Concrete light: Cool as all get out, but don't let that tish fall on your countertops...
Was man nicht alles mit ein bisschen Zement und Sand zaubern kann! #diy #selbstgemacht
The prototype. (bird). Could diy with fast drying concrete
ett la benn: Using Cellulose (plant material waste) and turning it into amazing bowls, light shades etc.