Cut the stems from the spider mum blossoms, leaving a 1-inch to 2-inch stub below the flower.
Insert a piece of floral wire up the stub of the stem and through the base of the flower. Twist the length of wire below the stub into a loose coil so you can lay the flower flat in the plastic container.
Spread about 1 inch of silica gel in the bottom of the plastic container, and lay the flower face up on top of the gel. When drying more than one flower, lay them out in a single layer.
Gently sprinkle silica gel over the flower, making sure the crystals get deep inside the blossom and between the petals. Continue sprinkling silica gel over the flowers until the entire blossom is covered by about 1/3 inch of crystals. Cover with a tight-fitting lid.
Check the flower after two days. If the petals are stiff and papery, gently remove the silica gel from the flowers by brushing the crystals aside with a soft paint brush. If the petals are still soft, replace the lid and let them dry for another day.
Straighten the floral wire, and wrap it with floral tape.