Harvesting Capiz Shell — From Sea to Decoration

Identify areas with natural populations of windowpane oyster (Placuna placenta), called 'kapis' in the Philippines. These shells grow on sandy or muddy sea floors in shallow parts of the sea—usually 1-3 meters deep at low tide. In the province of Capiz, especially in Roxas City and the municipalities of Ivisan, Sapian, and Pontevedra, the best harvesting grounds are in estuaries and shallow coastlines with soft substrate. Observe the signs: old shells scattered along the shore, clear water with a sandy-muddy bottom, and calm water flow. Make sure you have the proper permit from the Bureau of Fisheries and Aquatic Resources (BFAR) before harvesting—the harvesting of capiz is regulated to maintain the population.

Prepare all equipment before going out to sea. The main method of gathering capiz is walking in shallow water while feeling and sifting through the sand by hand or with a simple rake. For deeper areas (2-3 meters), a snorkel and diving mask are needed. Prepare baskets made of bamboo or plastic for collecting. Capiz harvesters typically walk while treading on the seabed and feel the shells under their feet — the thin edge of the shell is felt in the soft sand. Prepare covering clothing to protect the skin from the sun — harvesters are in the water for many hours.

Enter the water at low tide — this is the best time because the water is shallower and it is easier to see and feel the capiz shells. Walk slowly on the sandy bottom, using the soles of your feet to feel the thin round capiz shells buried under 2-5 cm of sand. When you feel the hard, flat shape of a capiz, bend down and pick it up by hand. Each capiz shell is usually 8-15 cm in diameter, roughly round, and very thin (1-2 mm). Be careful when handling them — the edges can be sharp. Place the collected capiz shells in a basket hung at the waist. A skilled harvester can collect 100-200 pieces in one working day (4-6 hours in the water).

Bring the collected shells to the beach and rinse them with seawater to remove sand, mud, and small organisms attached to the surface. Soak the shells in a large tub with clean seawater for 1-2 hours — this allows living organisms to come out from between the shells. Discard damaged shells — those with cracks, chips, or excessive thinness are no longer usable. Separate the shells by size: large (over 12 cm), medium (8-12 cm), and small (less than 8 cm). Large shells have the highest value in the market.

Each capiz shell consists of two valves (half shells) joined together at a hinge. To separate them, insert the thin blade of a knife into the edge of the shell near the hinge and gently twist to open. You can also leave the shells in the sun for several hours — the heat dries the hinge ligament, which makes it easier to open. Separate each half carefully so the thin shell does not break. Each half is a usable piece of capiz. The contents of the shell (soft tissue) are removed — traditionally they are used as food or garden fertilizer.

Raw capiz shell has a thin organic layer (periostracum) on the outside and remaining flesh on the inside that must be removed to reveal the translucent quality of the shell. Soak the separated shell halves in a water and salt solution (1 kilo of salt per 10 liters of water) for 24-48 hours. The salt helps loosen the organic matter. After soaking, scrub each shell with a soft brush to remove the remaining periostracum. Do not use acidic chemicals — capiz shell is calcium carbonate (aragonite), which dissolves in acid. Rinse with clean fresh water afterward.

Raw capiz shells have a slight curve. To use them as windows, lampshades, and decorations, they need to be flattened. First, soak the cleaned shells in warm water (not boiling — about 60-70°C) for 5-10 minutes to soften the shell slightly. While still pliable, place each shell between two flat wooden boards and apply even weight on top. Let it dry for 24-48 hours while pressed. The result is a flat, translucent piece of capiz ready for further processing. Be careful with the weight — excessive pressure will break the thin shell.

After flattening, spread the shells on a bamboo drying rack under the sun. Sunlight has a natural bleaching effect on capiz — the UV rays whiten the shell and increase translucency. Lay the shells out without stacking them, in a single layer only. Turn them over every few hours so both sides are equally exposed to the sun. Dry for 2-3 days in good weather. The finished capiz should be almost transparent when held up to light — like frosted glass. The color will become creamy white to light gold. Take the shells in when it rains and store them in a dry place.

Sort the dried and flat capiz shells by size and quality. Measure the diameter of each piece using a ruler. Categories: Extra Large (more than 15 cm) — most expensive, used in lampshades and large windows; Large (12-15 cm) — for chandeliers and decorations; Medium (8-12 cm) — for wind chimes and small ornaments; Small (less than 8 cm) — for mosaic work and crafts. Also check the translucency: hold each shell up to the light — the most valuable are those that are nearly transparent with no dark spots, cracks, or discoloration. Set aside the defective ones — they can still be used in mosaic work where they are cut and combined with other materials.

For specific products, cut the capiz shell into the required shape using metal shears or a sharp knife. Capiz is thin enough to be cut with shears when slightly damp. Mark the shape with a pencil on the surface of the shell before cutting. For round lampshade panels, use a template. For square or rectangular windows, cut straight using a ruler as a guide. The edges of cut capiz may be sharp — smooth them with fine sandpaper (grit 220-320). Do not use an electric saw — the vibration will shatter the thin shell. All cutting is done by hand.

Curing is the final step before storage. Soak the finished capiz shells in clean fresh water with a little baking soda (1 tablespoon per 5 liters of water) for 2-3 hours. This removes the remaining salt and neutralizes any leftover organic acids. Rinse with clean water and air-dry again for 24 hours in the shade — direct sunlight is not needed at this stage. Once dry, the shells may be coated with a thin layer of mineral oil using a soft cloth to enhance the luster and translucency. This is optional — shells without oil have a more natural matte finish that some craftsmen prefer.

Pack the finished capiz shells carefully to prevent breakage during transport. Place a thin layer of paper or cloth between each shell so they do not scratch or stick together. Stack shells of similar size in bundles of 50-100 pieces, wrapped in soft paper and tied with cord. Place in a box with extra padding on the sides. Store in a dry area with good ventilation — capiz shell can become brittle when too dry or develop an odor when stored in humid areas. The proper storage temperature is 20-30°C with humidity below 60%. Properly stored capiz shell will last for many years without loss of quality.