Preserving flowers with drying agents yields a three dimensional flower with good color and shape. The flowers will last three to four years or more untreated, and much longer if treated with a spray sealant. Dried flowers sometimes reabsorb moisture from the environment, especially in humid climates. For best results, store and display dried flowers in a covered container to inhibit moisture and dust.
The best drying agent for flowers and foliage is silica gel. Silica gel is readily available in most garden and hobby shops. It rapidly absorbs the moisture and preserves more of the color than other drying agents. Flowers dry in two to four days in a sealed container.
Flowers dry well in clean, dry sand. Use a very fine, salt-free sand. Dry the sand in a thin layer, on a baking sheet, at 250 degrees for 30 minutes. Allow the sand to cool before using. Dry the flowers in an open container in a warm, dry place. Flowers dried in sand will take much longer to dry, up to three or four weeks, depending on the flower. Sand-dried flowers are fragile, so use care when handling them and store them in a rigid, sealed container.
Borax is often used in a mixture with cornmeal, sand, oatmeal, cream of wheat or powdered pumice. Mix one part borax with one to five parts of cornmeal or other carrier material. Different mixtures work best in different environments. Start with 50 percent borax and adjust it to find what works best. Dry the flowers in an open container in a warm dry place. Flowers dried in borax mixtures will take one to three weeks to dry.