mussel shells

SHELLS + alginate composite
- recipE -


  • grinded musselshells
  • 7,5% (m/v) sodium alginate solution
  • 2% (m/v) calcium chloride solution


  1. clean the shells
  2. remove the periostracum (optional)
  3. grind the shells
  4. prepare the alginate solution
  5. mix and mold
  6. post treatment: cross-linking



  • After cooking the mussels, clean the shells removing the muscle and any residual organic part with the help of a knife

remove the periostracum (optional)


To remove the dark layer that covers the shells and make them easier to grind in the following step:

  • Wearing gloves, in a basin prepare a sodium hydroxide solution weighing 0,2 parts of sodium hydroxide in 10 parts of water
  • Soak the shells and leave them 3-5 days in the solution. Water will turn darker as the periostracum pieces detach from the shells. The shells become more brittle.
  • With the help of gloves and an abrasive pad remove the dark film that covers the shells and rinse them
  • Let the shells air dry

grind the shells


In sodium hydroxide pre-treatment (see step 2 – optional-), the shells become more brittle. You can also put them in the oven for a while to make them easier to grind.

  • I normally use a mortar to start breaking the shells
  • You would need a blender to make a finer powder. My advice is not to use an expensive one cause the shells can be tough to grind and it could get damaged
  • Using strainers with different sizes of the holes you get coarser of finer powders. 1mm mesh size is good.



  • Pour water into a tall container with a lid and add the alginate
  • Mix well with a whisk. It can help you closing the lid and shaking the container for a couple of minutes
  • Leave the solution in the fridge overnight to make it homogeneous and to let out the air bubbles



  • Weight the shells powder and the alginate solution.

With 3 parts of grinded shells (e.g. 300gr) and 1 part of alginate solution (e.g. 100gr) you get a compound you can mold with your hands. Decreasing the percentage of powder (up to 1 part of shells and 1 part of alginate) you get a less dense consistency more suitable to be poured into a mold

  • Mix well with a spoon to make the mixture as homogeneous as possible
  • Mold the mixture into a shape
  • Let it air dry. You can also use a dehydrator or put the pieces in the oven at 35°C to shorten the drying time. The more liquid is the mix, the more it will tend to crack if subjected to temperature changes



  • Prepare a 2% calcium chloride solution with water
  • Dip the shells composite in the calcium chloride bath for 10-20min
  • Let it air dry. It is now water resistant (but will absorb water if soaked)
in water
in calcium chloride solution