from The Ultimate Book of Kid's Concoctions
You can create sand castles and sand sculptures that are permanent.
1 cup sand
1/2 cup cornstarch
3/4 cup liquid starch
1. Combine sand and cornstarch in an old pot.
2. Add liquid starch and mix.
3. Cook the mixture over medium heat while stirring constantly. Eventually, the mixture will thicken and turn to dough.
4. Remove the pot from the stove and let the clay cool.
5. Remove clay from the pot and knead it for 20 to 30 seconds before using.