Preserving seashells is a simple process. Preserving seaweed is a more complicated and delicate task. A simplified procedure can give you good results with seaweed. The best delicate, artistic mountings of finely filamented seaweed samples is an art form that takes practice and patience.
Make sure that there are no living creatures in the shells you collect.
Soak the seashells in a mixture of half water and half bleach for several days. Thoroughly rinse and dry the shells in sunlight.
Apply mineral oil to give the shell lustre. You may use either a small brush to apply the oil or dip the shell in a container with mineral oil.
Place mounting paper in processing tray and cover with 1/4 of an inch of seawater. Center the seaweed sample on the paper and use tweezers to position the fronds as you want them.
Remove the mounting paper carefully from the tray and place on newsprint or blotting paper to drain. If you have trouble removing the paper without dislodging the sample, try draining the seawater out with a turkey baster before removing the mounting paper.
Cover the mounted seaweed sample with waxed paper, corrugated cardboard and the wooden board. Add weight to the top of the board, such as books or bricks, to press the seaweed sample.
Check the press daily and add fresh, dry newsprint or blotting paper beneath the mounting paper until it is completely dry. Then carefully remove the waxed paper and apply glue to secure any parts of the sample that are not firmly attached to the mounting paper.
If you intend to use shells as part of a larger display, use shellac instead of mineral oil to give the seashell its final lustre. Mineral oil will make shells hard to glue. A kitchen cutting board is sized properly and will work well for pressing seaweed.
You should transport seaweed in seawater. Placing it in fresh water can cause discolouration.