May 



1902.] 



THE INDIA RUBBER WORLD 



257 



SPONGE RUBBER AND RUBBER SPONGES. 



SPONGE rubber, known also as " moss rubber " or " frost 

 rubber," is by no means a new discovery. Common re- 

 port has it that it was first manufactured in England and 

 later in France and Germany. The value of the spongi- 

 ness of vulcanized rubber was, however, fully recognized by 

 Goodyear, who made sponge cord for weather strips. He also 

 vulcanized a sheet of sponge rubber between two air-tight 

 fabrics, cutting the sheets apart later and using the "shag" sur- 



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SPONGE RUBBER. 



face for bath mittens and the like. A suggestion of his, that 

 is of value only as showing the thought he put upon this sub- 

 ject, is the manufacture of rubber carpet with a spongy surface 

 and cloth backing, which should be softer to the tread than the 

 " finest velvet." 



The uses to which sponge rubber are put are many 

 and varied. It is used as a cushion for rubber stamps, in 

 artificial feet, in playing balls, in semi-solid tires, for erasive 

 rubber, for glove cleaners, and it has been tried in horse 

 collars, harness pads, cushions, and so on. In all cases the 

 sponginess is induced by incorporating something that will 

 give off vapors during the process of cure. Of course the very 

 cheapest liquid for this purpose is water ; hence one of the first 

 compounds for puff balls depended upon its dampness for 

 sponging. It was as follows : 



Soft African rubber 5 pounds . 



Reclaimed rubber. ... 5 pounds . 



Whiting 6 pounds. 



Litharge 2 pounds . 



Palm oil I pound. 



Sulphur s'A ounces . 



Damp saw dust 2 pounds . 



The sawdust was just fine enough to pass through a sieve 

 of No. 20 mesh. It was thoroughly wet and the mixing done 

 on a cool mill. A slow cure and the cooling of the molds 

 before opening are of course necessary. Compounds similar 

 to this where fiber, substitute, etc., are made the means of 

 carrying the water are veiy common and are exactly as good 

 for the purpose. Quite a variety of ingredients are used in 

 some of the spongy compounds, but none will appear to the 

 rubber manufacturer to be more novel than brown sugar and 

 licorice, both of which bring about sponginess. Perhaps 

 the most distinctively " freak " compounds in this line are 

 those that follow, and have been the subjects of British 

 patents : 



NO. I. 



Para rubber . .50 pounds. 



Tungstate of soda ... 9 pounds. 



Alum 2 pounds. 



Carbonate of ammonia. 14 pounds. 

 Asbestos (fine powder). 23 pounds. 



Arsenic i pound. 



Gum Kauri i pound. 



NO. 2. 



Carbon, of ammonia. 15}^ pounds. 



Alum 3 pounds. 



Tungstate of soda. .. 3 pounds. 



Borax 5 pounds. 



Camphor loj^ pounds. 



Lampblack. ..... ..10^ pounds. 



Para rubber 50 pounds. 



Sulphur 2>^ pounds. 



NO 3. 



Alum 6 pounds. 



Tungstate of soda 6 pounds. 



Chloride of ammonium 12 pounds. 



Borax 8 J^ pounds. 



Camphor 6 pounds. 



Lamp black 8 3^' pounds. 



Para rubber 50 pounds. 



Sulphur 2 >^ pounds. 



It will be seen from the foregoing that it is the easiest matter 

 in the world to cause rubber to " sponge." But to make a per- 

 fect rubber sponge, such as are to-day sold the world over, and 

 which only one company as yet has produced, is quite a dif- 

 ferent problem. And this is because the trade demands a rub- 

 ber sponge that is odorless, that is evenly spongy, and one that 

 will not harden after lying in stock for a month or two. A 

 large amount of experimenting is now going on in a score of 

 factories, and as the market grows so will new manufacturers 

 learn the secret and be able to supply the goods. Indeed, this 

 is to be wished for, as to-day rubber sponge sells for too high a 

 price and holds its place in the market simply because it is far 

 superior, for many uses, to the natural sponge. 



Hancock, in experimenting for sponge effects, made a benzol 

 solution of Pard rubber and stirred into it just enough of the 

 Parkes cold cure solution to cure very slowly. Then he im- 

 mersed the vessel in water heated just to a boiling point, leav- 

 ing it there until the solvents were fully volatilized. This re- 

 sulted in a beautiful sponge, but it was far from odorless and in 

 time grew as hard as a rock from the effects of the sulphur 

 chloride. A later modification of this process was to heat the 

 solution of rubber until it sponged and then dip it quickly into 

 the chloride solution, killing the continued effect of the chlor- 

 ide of sulphur by the ammonia and water bath. 



Rubber sponges have been offered in the American trade at 

 various times, but with little success until recently. With the 

 introduction of a really excellent article, however, the demand 

 has grown rapidly and still continues to grow. 



A RUBBER SPONGE. 



