December I, l'3iO 



THE INDIA RUBBER WORLD 



167 



Dry Heat Varnishes and Their Manufacture 



THK MAXUFAtf IKE of variiish tor dry heat goods, such as 

 footwear and surface clothing, is really an oil-boiling prop- 

 osition, and does not cail for the huge chimneys nor the re- 

 torts of the old-time gum varnish maker. In boiling linseed oil, 

 large kettles are used, the cold oil occupying one-third of the in- 

 terior, and even then it sometimes boils over. The varnish house 

 with its inflammable contents is as carefully segregated from 

 other buildings as is a cement and naphtha house. 



In preparing the oil varnish, the principal point is getting the 

 fluid up to about 300 degrees F. and as quickly as possible and 

 holding it there for several hours. The final stage is an in- 

 crease of heat that causes frothing or boiling. This is con- 

 tinued until the liquid becomes viscid. 



Back in the beginning of rubber shoe manufacture, what 

 •was known as the original Goodyear varnish was used. The in- 

 gredients were : 



Linseed oil, boiled thick 10 gallons 



Sulphur 10 iiounds 



Pulveriied rosin 45 ounces 



Campheni' 10 gallons 



N^phtl-a 15 gallons 



The oil and rosin were first mixed together cold and heated 

 up t(j 290 degrees 'F. The sulphur was then added and allowed 

 to stand 40 minutes. Ne.xt, the heat was run down to 215 or 

 220 dcsrce> 1'. and the camphcne added. Then the heat was 



Frickson's Shoe Varnishing Machine 



run down to 150 degrees, the naphtha added and let stand until 

 cold. Lastly, enough naphtha was added to bring it down to 

 50 gravity. 

 A more modern formula is : 



Best raw linsoed oil -'2 callons 



White sugar of lead : ■ -A'A pounds 



Boil these ingredients together until the oil is "thick and viscid, 

 and let it stand until cold. Then take 12 gallons of the above and 



heat it up to 290 degrees and add 7'/2 pounds of sulphur. Keep 

 stirring and let the heat run up to 360 degrees. Then let it stand 

 for 30 minutes. Then run the heat d<jwn to 150 degrees. Add 12 

 gallons of naphtha, and keep stirring until it gets cool. 



\\'au,'.s Shoe X'arnishing Maihine — 1.\ I'u.^riKJN for Dipping 



.\ rubber shoe varnish used in Norwegian mills is made 

 as follows : 8 kilograms of linseed oil, to which are added 1,170 

 grams of sulphur. Mix 8 grams of rosin with 40 grams of mag- 

 nesia or 50 grams of lime, and add to the first mixture. 



\ very cheap shoe varnish is : 



Well boiled linseed oil 10 gallons 



Sulphur 10 pounds 



Naphtha, 62 gravity 34 gallons 



Primarily, rubber boots and shoes on lasts or trees were given 

 the varnish coat by a broad brush in the hands of a skilled var- 

 nisher. Later, a dipping trough was used, in which each shoe 

 was carefully immersed, slowly drawn out and drained before 

 placing on the heater car. This, in turn, was displaced in 1906 

 by the Erickson varnishing machine. This in brief was a varnish 

 tank fitted with an agitator to keep the varnish in homogeneous 

 solution. A rack of ten shoes placed in the upper part of the 

 tank was slowly revolved, dipping all of the shoes at once and 

 giving each an even coating of varnish. With this machine foi4f 

 men could do the work of ten by the hand dipping process. 



Two years later the Wall machine appeared. This needed 

 but two men to operate it. In operation a stick of eight shoes 

 is clamped over the varnish tank, a lever pulled, and the shoes 

 descend into the varnish, are raised up by counter-weights and 

 automatically transferred to a draining rack. Operated by one 

 man, 500 pairs of shoes an hour are varnished. Two men, how- 

 ever, can handle 1,200 pairs, so it is naturally a two-man machine. 



CARRIAGE CLOTH, AUTO TOP, AND SURFACE CLOTHING 

 VARNISHES 



Rubber automobile top cloth and carriage cloth are given a 

 coating of vulcanizing varnish, often containing a pigment, which 



