This clay is made from ordinary beach sand and is great for decorating cheap picture frames (I get wooden ones from the $1 store) to remember trips to the beach.
1 cup sifted beach sand
1/2 tsp alum
about 1/4 cup corn starch
1 cup water
Combine ingredients in an old, heavy saucepan. Stir "constantly" over medium heat. When clay starts to stiffen and hold its shape a bit, remove from heat and turn onto foil until it is cool enough to work with. It cools very quickly, so you will want to mold it soon for best results. The clay can be molded into shapes or around picture frames, bookends, etc.
To make a sand frame, take the glass and backing out of a cheap wooden frame and set aside. Follow the recipe above for the clay. Spread glue on the frame one section at a time.
Press the clay onto the frame about 1/2 inch thick. Press clay together until the whole front of the frame is covered and all smoothed out. Be sure to scrape any excess off so the glass will fit back in when the clay hardens.
Now spread glue on the back of small shells, bits of beach glass, or stones and press gently just a small way into the clay. Fill any cracks in the clay as you go.
Let the frame harden for at least 2 days. When it is completely dry, it will be like concrete, but looks just like beach sand!
Now spray with a clear, matte finish craft sealer (about $2 a can at the craft store), replace the glass and backing, and insert your favorite vacation pic.