You can purchase fabric stiffener at a craft store, or simply use white craft glue.
From the thestate.com
The Halloween ghost can be created with a cheesecloth and fabric stiffener.
From the thestate.com
The Western European Union, set up in 1948, was a cold war spine-stiffener.
From the economist.com
Soak each piece of fabric in the stiffener and squeeze out the excess.
From the thestate.com
She cut out the pattern and applied an iron-on stiffener to the back.
From the charlotteobserver.com
It is Mr Mandelson's loss as an adviser and back-stiffener that Mr Blair will feel more keenly.
From the economist.com
It's also a fantastic stiffener.
From the independent.co.uk
It's 100 percent polyester, but it has been sprayed with a vinyl stiffener, which gives the shade body and allows it to be cleaned with a damp sponge and a mild household cleaner.
From the kansas.com
A cook's palette knife eases the moulded crown off the block and, straying into bathrooms, a bottle of nail varnish remover is an emergency remedy for removing excess stiffener.
From the guardian.co.uk
More examples
Material used for stiffening something
Anything added to something in order to stiffen it, such as a support beam, or starch for a collar
(Stiffeners) Thinner stands used as extra support for the top planks of a narrowboat.
A member used to strengthen a plate against lateral or local buckling.
A structural or fabricated angle iron shape, attached to the exterior surfaces of a duct or bulkhead at specified intervals for the purpose of reinforcing the metal and to prevent vibration.
A thin mill-board used for various purposes.
In a case binding, a strip of paper or thin card, cut to the width of the spine, placed between the boards and glued onto the covering material to stiffen or strengthen the spine cloth.
A compounding material used to increase the viscosity of an unvulcanized rubber mix.
An angle, a T, a plate, or another rolled section that is riveted, bolted, or welded on the web of a plate girder or another built-up member to transfer stress and prevent buckling or other deformation