A day before, prepare a 2% alginate solution by mixing 200ml of water with 4 grams of alginate. Leave the alginate solution to hydrate for 24 hours.
In separate pots, boil the eggshells and prawnshells for 10 minutes in order to clean them. Drain the pots and place the cleaned shells in the oven for 15 minutes at a temp of 45-50 degrees celsius to dry them. Once dry, grind the eggshells and prawn shells into fine particles.
Mix the shells with 45 grams of the hydrated 2% alginate solution. Stir gently until they mix completely avoiding the incorporation of bubbles.
Put in a mould and then gently pour vinegar over the top. It will start reacting and coagulating. Leave it to react for 15 minutes and then try to separate the mix from the mould gently in order to leave space for the vinegar to penetrate the sides. Wait for an hour. Then take the sample out of the mould and turn it around to allow the vinegar to reach the other side of the biocomposite. Leave it for another hour.
Take it out of the mould, rinse it under tap water to clean the vinegar off and leave it to dry. The sample shrinks in size from it’s gel state to it’s dry state which feels ceramic-like.