COMMERCIAL SPONGES 737 



comparatively, but not wholly, free from embedded sand and other siliceous 

 matter, which imparts to some closely related species a harshness and makes 

 them unfit for domestic and industrial use. The network formed by the fibers is 

 composed of small, close meshes. The qualities affecting the commercial value of 

 sponges are color, size and shape, softness, fineness, durability, resiliency and 

 absorptiveness. 



Color is the consideration of least intrinsic importance, though for esthetic 

 reasons it exerts considerable influence on the market value. As the color is often 

 incidentally correlated with other qualities, due to local conditions, it is of value 

 in distinguishing the grades and geographical varieties. 



Size and Shape. The most desirable size (and to some extent the shape) depends 

 on the use to which it is to be put: For surgical and some toilet purposes small 

 ones are desired; for the bath a medium size; while for cleaning vehicles a large 

 sponge holding a considerable quantity of water is necessary. Sponges up to 8 

 inches in diameter are commonly used entire and called "forms"; while large ones 

 or those that are irregular or torn are usually cut into pieces called "cuts." 



The valuable commercial sponges are regular, more or less massive, and free 

 from long processes or "fingers." They are spheroidal, cake-shaped, conical, or 

 cupped; a great many are of intermediate shape. For general purposes the more 

 desirable forms are the spheroidal and cake-shaped; but for such work as applying 

 glaze to pottery a flat surface is desired, and this is generally obtained by cutting 

 up a massive form or by using pieces of a smooth-surfaced lamellar sponge, like 

 the Mediterranean elephant's ear. 



The more desirable grades of sponges are those which are softest. Sponges 

 with comparatively slender fibers, with the microscopic meshes rather open, with 

 a small amount of foreign matter embedded in the spongin, and with an open 

 canal system are the softest. Those with the fibers laden with sand are invariably 

 harsh. 



Fineness depends upon the macroscopic rather than on the microscopic arrange- 

 ment of the skeleton, though the slenderness of the fibers is a factor. The Mate- 

 cumbe sheepswool is one of the softest sponges, but its open structure makes it 

 appear coarse when compared with Mediterranean kinds. Fineness in the same 

 species, like other qualities, varies more or less with the environment under which 

 the individual is produced. Toughness and durability vary greatly with the species, 

 and in the same species, with the conditions under which the sponge grows. 



Resiliency. Resiliency is the property of sponges which causes them to recoil 

 after being pressed. It depends on the size and the arrangement of the fibers and, 

 to a certain degree, on the method of curing and thoroughness of cleaning. Sponges 

 which rapidly regain their original shape after compression are much more useful 

 than those which are sluggish in their reaction. 



Absorptiveness. The ability to absorb and retain a large volume of water is the 

 fundamental quality which determines the usefulness of a sponge. Sponges with 

 fine meshes, slender fibers, and a close texture absorb more water than those with 

 large canals and big cavities. Absorptiveness depends on a combination of other 

 qualities, namely, softness, fineness, and resiliency. The fibers themselves absorb 

 only a small amount of moisture, the water being held primarily by the capillary 

 action of the sponge skeleton. 



