Sand dollars are the skeletal structures, or tests, of a type of flattened sea urchin composed primarily of calcium carbonate. When these tests wash ashore after the animal’s death, they frequently retain residual organic tissue and algae, leading to a gray, brown, or even black coloration. This discoloration results from the decomposition of the animal’s soft parts and residual marine growth embedded within the porous structure. Collectors aim to remove this embedded organic material to achieve the smooth, clean white appearance desired for display and long-term preservation.
Preparing the Sand Dollar for Treatment
The process begins with a gentle physical cleaning to eliminate loose debris like sand, dirt, and any remaining spines. Use a very soft tool, such as a fine-bristled paintbrush or a soft makeup brush, to carefully sweep the surface of the sand dollar. The test is exceedingly delicate, so handling should be minimized and performed over a cushioned surface to prevent accidental breakage.
After the initial brushing, the specimen requires a freshwater soak to help leach out residual salts and organic matter. Place the sand dollar in a shallow, non-metallic container and pour tap water over it until it is fully submerged. Allowing the specimen to soak for several hours facilitates the removal of internal debris.
The water should be changed when it becomes noticeably murky or discolored from the released salts and particulate matter. Removing the salt residue is beneficial because it prevents interference with the subsequent chemical whitening step.
Applying the Whitening Solution
The whitening process relies on hydrogen peroxide (H₂O₂), which functions as an oxidizing agent. Oxidation chemically breaks down the dark organic pigments and residual soft tissues responsible for discoloration. This chemical action lifts the stains from the porous calcium carbonate structure.
Use the standard 3% hydrogen peroxide solution for this procedure. Place the pre-cleaned sand dollar into a clean container and pour the solution over it until the specimen is completely submerged. Full immersion is necessary to ensure the bleaching action is uniform across the entire surface of the test.
The required soaking time depends on the initial degree of discoloration and the thickness of the sand dollar. Lightly stained specimens may whiten in just a few hours, while darker pieces may need to remain submerged overnight to complete the oxidation process.
Monitor the sand dollar periodically, checking for a uniform white color to prevent over-soaking. Keep the container in a location with good ventilation, away from direct sunlight, throughout the soaking period. Wearing gloves is advisable to protect the skin from the oxidizing effects of the H₂O₂ solution.
If the sand dollar tends to float, place a small, non-metallic object gently on top to keep it submerged. Maintaining full and consistent contact with the hydrogen peroxide ensures that the whitening occurs evenly, avoiding patchy or mottled results.
Final Drying and Sealing
Once the sand dollar is uniformly white, thoroughly rinse it to neutralize the hydrogen peroxide. Rinsing the specimen in fresh water removes residual H₂O₂ and stops continued oxidation that could weaken the structure. Place the specimen on an absorbent material, like a clean towel, to begin air-drying.
Drying should occur in a well-ventilated area away from direct sunlight. Direct sunlight can cause the test to dry too quickly, increasing its brittleness and susceptibility to crumbling. Allowing it to dry slowly prevents damage to the delicate structure.
The final step involves applying a protective coating, as chemical whitening makes the delicate test more susceptible to flaking and breakage. Use a diluted craft glue solution or a clear matte acrylic spray sealant.
This sealant penetrates the porous matrix, bonding the tiny spines and particles together to increase structural integrity for long-term display and handling.