According to the experts at Silk Road textile merchants: "Silk organza is a sheer, thin open weave fabric that is heavier and crisper than silk gauze. It has a smooth, flat finish, is strong and durable, and gets its stiffness from tightly twisted yarns... Silk organza is very lightweight and sheer, but a bit stiff, and can be gathered for bouffant uses, used alone or over other fabrics." Thus, when it must hold a fold, it is best to apply a water-soluble fabric stabiliser to help it maintain stability.
Place the organza in the position that you want it to be in. Hold it in place with a safety pin or sew it if this is for a craft project. If not, make sure that it is lying flat.
Spray the organza with the water-soluble fabric stabiliser. If you just need the organza to be slightly stiff, a few sprays should be adequate: spray directly above the fabric, creating a mist. Let the mist fall on the organza. If you need the organza to be extremely shaped and styled and very stiff, then spray it heavily directly on the fabric.
Let the organza dry for 10 minutes or according to the directions on the spray bottle. Gently test the dryness and stiffness of the fabric by gently nudging it with your pinky finger or fingernail.
Continue to use or style the organza as needed. Spray again if the fabric begins to wilt or loose its strength.
Water-soluble fabric spray is washable if you want to return the fabric to it's original style.
Always double check that the fabric stabiliser you use is suitable for organza.