To make homemade fabric stiffener, mix together equal parts of white glue and water, or mix flour or cornstarch with cold and boiling water. When mixing the flour or cornstarch mixture, mix it with the cold water first, and then stir it into the boiling water.
The glue mixture yields the whitest color, so it is probably best for white fabrics or lace. The stiffness from the glue mixture lasts the longest, but also takes multiple washings to get the fabric soft. In contrast, the cornstarch and flour mixtures wash off more easily, but the stiffness does not last as long. The flour mixture also creates a vintage look for the fabric.