Create permanent sculptures out of fabric using liquid fabric stiffener, available from craft stores under several different brand names. Fabric stiffener is a thick glue formulated especially for stiffening fabric permanently. Hang sheets of stiffener-covered fabric from a clothesline to turn them into flat boards or drape over a mould like a balloon or cardboard box. Your fabric assumes the shape of the mould and retain that shape permanently.
Cover your work surface with newspaper or a plastic garbage bag. Put on rubber gloves to protect your hands.
Fill a large plastic bowl with enough liquid stiffener to cover your fabric.
Submerge the fabric in the stiffener. Squeeze the stiffener through the fabric with your hands to saturate it completely.
Wring the fabric over the bowl to squeeze out any excess stiffener.
Shape the fabric over your mould or hang it to dry.
As an alternative, you can paint fabric stiffener onto the fabric using a paintbrush. Humidity can affect drying time and stiffness. Work in a low-humidity area to ensure best results.