Sponges are animals belonging to the group of Porifera (Phylum Porifera), a name which derives from the Latin
porus and ferre which means "bearers of pores. They are Metazoans, meaning multicellular animals
but with a rather simple body organization. In fact they do not possess actual tissues but rather
individual cells specialized in performing functions such as the construction
of the elements of the skeleton, nutrition and reproduction.
Ecologically sponges are typically benthic (they live on the seabed)
and are almost exclusively marine. There are very few species of fresh water sponges.
They feed by filtering water and retaining nutrients which consists mainly of micro-algae,
bacteria and protozoa transported to them internally by an interwoven network of channels.
Being predominantly asymmetric, their body shape is extremely varied, in fact, they can
be encrusting, meaning a reduction in thickness with a large surface area, tubular-like hollow tubes,
like cushions or vases. Even their colours and sizes are also very variable with bright colours
(yellow, blue, purple, orange, red ...) with sizes ranging from a few millimetres
to a few meters in length. To date about 9000 species have been described.
The Phylum Porifera is divided into three distinct classes based on the characteristics of the elements
that constitute their skeleton. There is the Calcarea class species whose skeleton
is formed by calcium carbonate (CaCO3). The Hexactinellida class with siliceous skeleton sponge
(silicon dioxide SiO2) and the Demospongiae class consisting of sponges whose skeleton is mostly
made up of a network of organic collagen from a structure-derived protein called spongin.
It is the peculiarities of the skeleton of these sponges (Demospongiae) which is of commercial interest,
used since ancient times as hygiene products, and personal care.
The most well-known and appreciated sponge used for personal care is the Mediterranean sponge Spongia officinalis (Linnaeus, 1759), the use of this sponge was documented as early as the fourth century BC.
For everyday use, the natural sea sponge used as a bath sponge should be cleaned after each use under running water. The water should never be too hot (never exceed temperatures above 50°C), to prevent any soap or bath liquid residue that can corrode the sponge and make it slippery and weak. It should be left to dry after it is squeezed with care, so as not to generate the maturation of mold and preserve its long duration. It is better to leave it to dry in a ventilated area, this also allows a longer duration.
To eliminate the sense of viscosity which is possible when the sponge was not well cleaned after use, or to brighten the colour, add a spoonful of sodium bicarbonate to a container of warm water of dimensions slightly greater than that of the sponge. Dip the sponge and squeeze it for a couple of times, then leave it in the container for half an hour at most. After the soaking time, rinse the sponge and leave it to dry naturally.
If your concern is to make it sterile, the sponge can be immersed in water with a tablespoon of antibacterial disinfectant for an hour.