Table 17.— Elasticity 



Type of sponge 



Number of 

 sponges tested 



Average 



Standard 

 deviation 



Fiducial 

 limits 







Percent 



Percent 



Percent 



Hudson Grass 



25 



97.6 



2.U 



96.6-98.6 



Inshore Sheep swool 



26 



8U.3 



12.1* 



80.U-96.5 



Florida Yellow 



2U 



95.2 



2.9 



9U.O-96.U 



Anclote Grass 



2k 



9U.9 



3.U 



93.U-96.3 



Mediterranean Bengasi 



2$ 



78.1 



6.U 



75.5-96.3 



Rock Island Sheepswool 



28 



91.5 



9.U 



87.8-95.1 



Mediterranean Deepwater 



28 



69.8 



11.8 



62.2-7U.1; 



F. Shape-recovery testing allows the sponge 2 minutes to recover 

 its original size. If the sponge does not spring back immediately on 

 repeated fast squeezing during washing, however, this slow spring- 

 back does not mean that a few minutes of soaking will still leave it 

 without good recovery of shape. Nor does a slow return at the end of 

 2 minutes mean that the sponge has become "dead" or *not springy." 

 None of the sponges are really poor in this respect at the end of 2 

 minutes, and it was observed that with repeated wettings, the slow 

 shape recovery of the Mediterranean Deepwater sponges (table 18) is 

 not progressive or ever permanent. This test cannot therefore be 

 called a "permanent set" test in the scientific mea n ing of the words* 

 By accidentally drying some sponges at too high a temperature and 

 also by squeezing sponges through steel rolls at high pressure, the 

 author obtained sponges that were "dead." In short, they took such 

 a high permanent set that they resembled a wet cloth and were practi- 

 cally worthless. Aside from the Deepwater Mediterranean, all the 

 sponges had a high recovery of shape in 2 minutes* 



Summary of water properties . — A summary of water properties does 

 not reveal any one outstanding type of natural sponge, but these quan- 

 titative tests (the first ever published) should" enable a buyer to pick 

 the type of sponge he needs for a particular property. These tests 

 agree well with the sensory tests that have been used for many years, 

 in these particulars: 



1. The choice of natural sponges for commercialization is veri- 

 fied in that all show useful properties. No one sponge is superior 



in enough properties to justify the exclusion of others from the trade. 



2. The softness of the Mediterranean Deepwater sponges and the 

 stiffness of the Grass and Florida Yellow sponges are confirmed. 



h$ 



