Preserving a sand dollar comes down to a few straightforward steps: soak it in fresh water, gently clean off organic material, bleach it briefly, let it dry completely, and seal it with a hardener. The whole process takes a couple of days at most, and the result is a sturdy, bright-white keepsake that can last for decades on a shelf. Where people run into trouble is rushing the process, using too-strong chemicals, or accidentally collecting a sand dollar that is still alive. Each of those mistakes can ruin or discolor the specimen, so the details matter more than the broad strokes.
Make Sure It Is Actually Dead First
This is the most important step, and the one most often skipped. A living sand dollar is covered in thousands of tiny, velvety spines that give its surface a fuzzy texture and a dark color, usually brown, purple, or greenish-gray. If you flip it over, you may see its tube feet slowly moving. A dead sand dollar, by contrast, has lost most or all of its spines and feels smooth and hard to the touch. It is typically white or pale gray, sometimes with a faint greenish or yellowish tinge if it died recently.
If you pick up a sand dollar and its surface feels soft, fuzzy, or damp with a brownish residue on your fingers, put it back where you found it. Many beaches have regulations against collecting live sand dollars. In some U.S. states, taking a living one can result in a fine, because sand dollars are classified as marine invertebrates protected under shellfish or wildlife regulations. Beyond legality, there is no practical reason to collect a live one. Live sand dollars smell terrible during the drying process, the organic tissue is much harder to remove, and the result is rarely as clean as a naturally bleached specimen.
Soaking and Cleaning
Once you have confirmed the sand dollar is dead, the first real preservation step is a freshwater soak. Place the specimen in a container of cool, clean tap water and let it sit for several hours. If the water turns yellowish or murky, drain it and refill. This step removes salt, sand, and residual organic matter lodged in the tiny pores and channels that cover the test (the flat, disc-shaped skeleton). Sand dollars that have been sitting on the beach for a while may only need an hour; freshly dead ones benefit from an overnight soak with one or two water changes.
While it soaks, resist the urge to scrub it with a brush. The surface of a sand dollar is textured with a delicate petal-shaped pattern on the top and a series of grooves and pores on the bottom. Aggressive scrubbing can chip the thin edges or wear down the surface detail that makes the specimen attractive in the first place. If stubborn debris is stuck in the grooves, a soft toothbrush with gentle pressure works. Avoid anything stiffer.
Sand dollars found in tidal zones sometimes have organisms growing on them, including algae and small encrusting organisms like bryozoans or coralline algae. Research comparing recently dead sand dollar specimens with fossil ones has found that encrustation, particularly by coralline algae, is a common taphonomic feature of sand dollar tests in certain environments.1Palaeogeography, Palaeoclimatology, Palaeoecology. Taphonomic comparison between Recent and fossil sand dollars If you notice hard, pinkish or whitish patches growing on the surface that do not come off with soaking, the bleaching step usually takes care of them.
The Bleaching Step
After the freshwater soak, prepare a diluted bleach solution. A common ratio is one part regular household bleach (sodium hypochlorite, the plain unscented kind) to three parts water. Place the sand dollar in this solution and watch it. The specimen will start to lighten within minutes. Most sand dollars reach a uniform white in five to ten minutes. Do not leave them soaking for hours. Extended bleach exposure weakens the calcium carbonate structure and can make the test brittle enough to crumble in your hands.
A useful rule: pull the sand dollar out as soon as it looks evenly white. If it still has yellowish patches after ten minutes, remove it, rinse it thoroughly in fresh water, and try a second short soak in a fresh bleach solution later. Two short soaks are always better than one long one. Once it looks good, rinse it under cool running water for a full minute to remove all bleach residue, which can continue to eat at the surface if left on.
Some people skip bleach entirely and use hydrogen peroxide instead, particularly the 3% concentration sold in pharmacies. Hydrogen peroxide is gentler, though it works more slowly. It is a good choice for very thin or fragile specimens. Soak time with peroxide is longer, sometimes an hour or more, but the risk of over-bleaching is much lower.
Drying Properly
After rinsing, set the sand dollar on a flat surface in direct sunlight. A paper towel or a wire rack works well; avoid placing it on a colored towel that could transfer dye when wet. Sunlight does two things at once: it evaporates moisture and continues to bleach the specimen slightly, evening out any remaining discoloration.
Drying typically takes a full day in warm, sunny conditions. In humid or overcast weather, it can take two or three days. The sand dollar needs to be completely dry before you seal it. If moisture is trapped inside, it can cause discoloration or a musty smell over time. You can tell it is dry by weight: a dry sand dollar feels noticeably lighter than a damp one. Tap it gently with a fingernail. A dry specimen sounds hollow and resonant rather than dull.
Flip the sand dollar halfway through drying so both sides get equal air exposure. The underside, with its more complex surface texture, holds moisture longer than the smooth top.
Hardening and Sealing
An unsealed sand dollar is fragile. The skeleton is porous and relatively thin at the edges, and even a short drop onto a hard surface can crack it. Sealing it with a hardener dramatically improves durability and gives the surface a slight sheen that many people find more attractive than the chalky matte finish of raw bone.
The most common sealant is a mixture of white glue and water, roughly half and half. Brush it onto the entire surface with a soft paintbrush or a foam brush, let it dry, and apply a second coat. The glue dries clear and soaks into the porous surface, reinforcing it from within. Two coats are usually enough for a display piece. Some crafters prefer a spray-on clear acrylic sealant, which gives a harder finish and can add a slight gloss. Either method works. The key is full, even coverage on both sides.
If you want a natural, uncoated look, you can skip sealing, but handle the sand dollar as little as possible. Oils from your skin will gradually yellow the surface over time, and the specimen will remain breakable. For anything that will be handled by children or used in a craft project, sealing is worth the extra step.
Why Sand Dollars Are So Fragile
Understanding what you are working with helps explain why certain steps matter. A sand dollar’s test is not a shell in the way a clam or snail shell is. It is an internal skeleton that was once covered in living tissue and thousands of tiny spines. The test itself is made of interlocking plates of magnesium-calcite, a form of calcium carbonate with magnesium atoms substituted into the crystal lattice. Research on sand dollar skeletons has shown that different body parts have different mineral compositions at very fine scales: the teeth, for instance, show more variation in magnesium concentration than the test plates or spines.2Biogeochemistry. Detailed controls on biomineralization in an adult echinoderm: skeletal carbonate mineralogy of the New Zealand sand dollar (Fellaster zelandiae)
This mineral composition matters for preservation because magnesium-calcite is more soluble than pure calcite, especially in acidic conditions. That is why vinegar, lemon juice, and other acidic household cleaners should never be used on a sand dollar. They will dissolve the surface. Even prolonged exposure to bleach, which is alkaline but still chemically aggressive, can weaken the crystal structure. The goal of every cleaning step is to remove organic residue without attacking the mineral skeleton itself.
The edges of a sand dollar test are its thinnest points, sometimes barely a millimeter thick. The center, where the petal pattern is most pronounced, is thicker and stronger. When sand dollars break, they almost always crack from the edge inward or along the radial lines of the petal pattern. Studies of fossil sand dollars have documented radial cracking as a characteristic failure mode, caused in geological contexts by the weight of overlying sediment compressing the hollow interior.1Palaeogeography, Palaeoclimatology, Palaeoecology. Taphonomic comparison between Recent and fossil sand dollars The same structural weakness applies to a sand dollar sitting on your shelf: pressure on the flat face, especially from stacking, is more likely to crack it than gentle edge-on handling.
Common Mistakes That Ruin Sand Dollars
People who have tried to preserve sand dollars and ended up with broken, discolored, or smelly results usually made one of a few predictable errors:
- Over-bleaching: Leaving the specimen in bleach for an hour “just to be safe” can turn a solid sand dollar into something that crumbles when you pick it up. Five to ten minutes is the window for most household bleach concentrations.
- Skipping the freshwater soak: Going straight from the beach to the bleach solution means salt crystals are still embedded in the pores. As those crystals dissolve unevenly in the bleach, they can cause patchy whitening or leave rough spots.
- Collecting wet, recently dead specimens without adequate cleaning: A sand dollar that died within the last day or two still has soft tissue inside. If you dry it without thorough soaking and cleaning, the remaining organic material will decompose and produce an unmistakable rotten-seafood smell that can persist for weeks.
- Stacking or crowding during drying: Sand dollars stuck together while wet can bond to each other and break when separated. Lay them out individually with space between them.
Another less obvious mistake is using hot water at any stage. Hot water can cause the calcite plates to expand unevenly and crack. Stick with cool or room-temperature water throughout the process.
Displaying and Storing Preserved Sand Dollars
A properly dried and sealed sand dollar is stable at room temperature and normal humidity. It does not need special storage conditions. Direct sunlight over many years can yellow the surface slightly, so if you are displaying one in a window, expect some gradual color change. A shadowbox or a shelf away from direct sun keeps it looking white the longest.
For craft use, sealed sand dollars can be painted with acrylics, decorated with markers, or incorporated into resin projects. If you plan to paint one, skip the glue sealant and use a spray primer instead, which gives the paint a better surface to grip. For resin embedding, the sand dollar needs to be perfectly dry and fully sealed, because moisture trapped inside will cause bubbles in the resin as it cures.
If you are transporting sand dollars, especially mailing them, wrap each one individually in tissue paper and place it between two pieces of cardboard cut slightly larger than the specimen. Bubble wrap alone is not enough for the edges, which are the most vulnerable to shipping damage. A rigid sandwich of cardboard gives structural protection that cushioning alone does not.
The Five Small Bones Inside
If you have ever broken a sand dollar and found small, white, bird-shaped pieces rattling around inside, those are the jaws of the sand dollar’s feeding apparatus, a structure called Aristotle’s lantern. In life, the sand dollar uses these tiny calcified pieces to grind food. There are five of them, arranged in a ring, and they look remarkably like little doves, which is why coastal folklore calls them “doves of peace.”
When drying a sand dollar, these pieces can sometimes shift and rattle. That is normal and does not mean the specimen is damaged. If one falls out through a break or through one of the petal-shaped slots on the surface, you can glue it back in with a tiny drop of white glue or craft adhesive. Some people deliberately shake the loose jaws out and display them separately alongside the intact test.
Sand Dollars from Different Regions
Not all sand dollars look or behave the same during preservation. The classic round, flat sand dollar found along the Atlantic and Gulf coasts of the United States is usually from the genus Mellita, which has distinctive elongated slots (called lunules) cut through the test. Pacific coast sand dollars, often Dendraster, are thicker, more domed, and tend to be sturdier during handling. Tropical species can be larger and thinner, making them more fragile.
The preservation process is the same regardless of species, but the bleaching time and fragility vary. A thick Pacific coast specimen can tolerate a longer bleach soak than a paper-thin tropical one. If you are working with an unfamiliar species and are not sure how sturdy it is, err on the side of shorter bleach exposure and gentler handling. You can always soak it again; you cannot un-crack it.
In some parts of the world, including New Zealand and parts of Southeast Asia, local sand dollar species have slightly different mineral compositions in their skeletons, which can affect how they respond to bleaching.2Biogeochemistry. Detailed controls on biomineralization in an adult echinoderm: skeletal carbonate mineralogy of the New Zealand sand dollar (Fellaster zelandiae) In practice, the variation is small enough that the standard freshwater-then-bleach approach works across species. But if you notice a specimen reacting unusually to bleach, becoming chalky or pitting on the surface faster than expected, pull it out early.
Repairing a Broken Sand Dollar
Accidents happen, and a broken sand dollar is not necessarily a lost cause. If the break is clean, with two or three large pieces that fit together snugly, you can glue them back with cyanoacrylate glue (super glue) and get a surprisingly invisible repair. Apply a thin line of glue to one edge, press the pieces together firmly, and hold for thirty seconds. Wipe any squeeze-out immediately with a dry cloth.
For a specimen that has crumbled into many small pieces, repair is rarely worth the effort. The result usually looks obviously reconstructed and is still fragile. A better option for sentimental pieces is to arrange the fragments in a small shadow box or embed them in clear resin, which preserves the material without needing structural integrity.
Chips along the edge are the most common damage. You can fill small chips with a paste made of white glue mixed with fine white sand or baking soda, applied with a toothpick and smoothed flat. Once dry, it blends reasonably well, especially if you apply a final coat of sealant over the whole surface.