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.
Turn an old towel into a stunning concrete planter! It might seem like an expert's job but this planter is a very basic concrete project. Get more concrete towel planter ideas from our album and learn how to do it by heading over to the step-by-step tut