Sand dollars can be bleached white by simply using a common household bleach and fresh water. Placing them under the sun for a time will also help make the sand dollars whiter naturally.
Sand dollars are a species of burrowing sea urchins that are rounded and very flat. Also known as sea cookies or snapper biscuits, these creatures are related to the star fish and sea cucumber.
The sand dollar takes its name from the discs of dead sand dollars that wash onto shores and are bleached white by the sun. The white circular discs usually measures between 1 and 4 inches in diameter. The rules of harvesting sand dollars may vary among beaches, but most beaches permit the collection of the sea urchin as long as it is already dead.
Here is a simple way of bleaching sand dollars.
Soak the sand dollars in a container with fresh water. The fresh water will soon become murky and may also smell. Pour out the dirty water and replace with fresh water. Repeat the process until the water stays clear.
Place the sand dollars in a solution with 2 cups of water and 1 cup of household bleach. Soak the sand dollars in the solution for a maximum of 15 minutes then rinse them thoroughly. It is important not to overdo this step as bleaching the sand dollars too much will make them brittle and crumbly.
Soaking the sand dollars in the bleach solution strips off all of the organic matter attached to the shell, and the solution also makes them whiter. Placing the sand dollars in the sun can enhance the whitening effect.
Cleaning agents with acids should not be used on sand dollars because acids will easily dissolve the shells, which are made up of calcium carbonate. To preserve the sand dollar, acrylic paint, clear laquer, or a white glue and water solution can be used to coat it.