March 1, 1921 



THE INDIA RUBBER WORLD 



399 



PROCESSES OF DRYING. PREPARING AND CEMENTING 

 The process of repair in a well-cquippeil rul)bcr repair shop is 

 as follows : 



A boot or shoe is first carefully examined to see if a repair 

 can be made successfully. Considerable judgment is required, 

 for a faulty repair drives customers away. Granted that the 

 article is acceptable the first step in the work is thorough drying. 



2,000,000 Pounds of Rubber Shoe Jink; 

 500,000 Pounds Could Be Rep.mrf.d 



When rubber footwear repair becomes a fully established in- 

 dustry vacuum dryers will probably be employed. At present, 

 however, many simple expedients are resorted to. One of the 

 best is a hollow heated form similar to those used in hosiery 

 mills, over which the article is drawn, and which soon e.xpels all 

 moisture. Use is also made of compressed air or a blast from a 

 small electric blower. Drying is very important, for not only 

 will cement refuse to stick to damp rubber or frictioned fabric 

 but blisters form during the cure, from imprisoned moisture, and 

 the repaired section is just so much weakened. 



The boot, thoroughly dried, is put upon a "jack," such as 

 leather cobblers use, and the worn parts cut away down to the 

 solid surface of tread, or to the cloth and rubber underlay. All 

 dirt is brushed out with a stiff wire brush. To get a good sur- 

 face for cement adhesion, the sole part is roughened thoroughly 

 with a rasp or a revolving wire brush. The whole of the part to 

 be patched is then coated with a rubber cement containing sulphur: 

 in other words, a vulcanizing cement. The boot is then put aside 

 until the solvent in the cement has fully evaporated. This is done 

 three times ; not that the surface needs so many coats, but to 

 allow some of the cement to penetrate to the rag filler and the 

 friction and thereby give them additional strength. 



MOLD MAKING 



The next step is the preparation of a mold for tlie new sole. 

 Stock molds for this purpose arc made by mold makers in the 

 rubber centers in any style called for. They are of iron or steel 

 and engraved for any sort of corrugation. Some repairers have 

 turiv'd to a lead mold which they make themselves. The process 

 is very simple. A sheet of lead plate J^-'fch in thickness, slightly 

 wider than the Ijoot to be repaired is taken, and the middle of it 

 marked to show where the corrugations should appear. It is then 

 scored with a cold chisel, or a flat, suitably-engraved steel punch 

 1J4 inches square with a series of criss-cross channels not unlike 

 the tread of a new rubber shoe. The edges are then turned up. 

 either about a wooden form or about the sole of the shoe itself, 

 and a shallow lead mold is the result. The mold is warmed, the 

 surface painted with a thin soft soap solution and when dried it 

 is ready for use. 



SOLE STOCKS AND HOW APPLIED 



Unvulcanized stock for solo repair is of two distinct sorts: 

 That which mav come from the rubber shoe manufacturer and 



which is already of the proper thickness and, indeed, has the 

 corrugated tread from the soling calender ; and tire tread stock. 

 The latter is more available in that every accessory house carries 

 it. If tire tread stock is to be used the modus operandi is this : 

 Two pieces are cut from 1/16-inch tread stock, so as to get a 

 ,^-mch thickness. If, after being rolled into one solid sheet, air 

 blisters develop, they are punctured by a sharp awl. The doubled 

 sheet is then cemented on one side and thoroughly dried. When 

 this is done, the boot is placed ujiside down on the jack, the new 

 sole applied and rolled on hard with a hand-roller. Where the 

 edges come, a stitcher is run to help the adhesion in parts which 

 the roller cannot touch. The lead mold is then put upon the 

 sole and tied in place vvitli broad tapes. 



CURING 



It is now ready for the vulcanizcr. This is a chest through 

 which the steam circulates. The boot is put upon the hot-plate 

 and kept there until vulcanized. The steam pressure is from 40 

 to 60 pounds, according to the grade of rubber used. .\t 40 

 pounds pressure the temperature is 288 degrees F., quite sufficient 

 for curing average stock. Finer qualities require higher temper- 

 ature. The average time for curing is an hour and a half. .V 

 frequent tightening up of the clamps during the process aids in' 

 evening up low spots. 



BOOT HEEL REPAIR 



The repairing of the heels of rubber boots is very similar to 

 that of sole repair. If only the heel is to be repaired, it is cus- 

 tomary to slip an asbestos or other fabric protector over the foot 

 portion of the hollow last. This prevents the heat from afifecting 

 the sole and upper during the cure. The methods described are 

 admirably adapted for the tread section of all sorts of heavy rub- 



Shoe Rep.\!r U.vit in Tire Rei'.\ir Shop 



l)er footwear, including fishermen's and lumbermen's overshoes 

 and men's and women's arctics. 



MENDING UPPERS 



For mending a tear or a worn spot in the leg or upper of a 

 rubber boot the process is as follows : 



The portion of the surface surrounding the tear is rubbed with 

 any abrasive substance that will remove the varnish. The rough- 



