78 BELL SYSTEM TECHNICAL JOURNAL 



tests. In the fine clay-like texture there are more solid particles present 

 than in the water-sand type of texture and therefore there is more surface 

 available for the retention of the liquid in the former type of semi-solid 

 mass. Drainage is thus greatly retarded with the result that porosity is 

 materially lessened. The type of texture determines in a large measure the 

 ease of shaping and potential porosity of a wiping solder. 



Having examined elementary forms of solidification, attention may now 

 be focussed on the setting up of the wiped joint itself. In practice, the parts 

 to be joined are cleaned and fluxed. Circumferential paper pasters are 

 then applied to the sheath and sleeve to restrict the spread of the solder. 

 The splicer then pours hot solder from a ladle over the prepared parts and 

 catches the excess in a cloth held in contact with the bottom of the joint. 

 The caught solder is repeatedly pushed back around the cable with a wiping 

 motion to aid "tinning" or alloying and to distribute the heat. After a few 

 such operations the prepared surfaces can be seen to be thoroughly wetted 

 by the solder. At this stage a portion of the caught solder is mixed in the 

 ladle with more hot solder and the mass which now has a clay-like consist- 

 ency is poured on the joint and molded into place using cloth pads. WHien 

 solidification has proceeded to a condition where the solder can support it- 

 self in position, manipulation is stopped. From this point on, loss of heat 

 takes place by conduction away from the joint by the sheath and sleeve, by 

 radiation, and by air convection currents at the surface of the solder. As 

 a result of this combination of heat losses final solidification takes place in 

 the interior of the solder mass near the important sheath-sleeve junction. 

 The action that causes pipes to form in castings draws the eutectic from the 

 critical area between the sheath and the end of the sleeve. If the solder 

 has the proper characteristics there will be a shell of solder which does not 

 have interconnecting shrinkage cavities, drainage cavities or fissures due to 

 the wiping operation and the finished joints will be gas tight. If the solder 

 is unduly coarse or has insufficient liquid eutectic at the time the mass is 

 too rigid to manipulate further, the resulting joint may leak. 



The new fillet wiping technique is similar to the old up to the step where 

 the splicer molds the mass to shape. At this point the new technique con- 

 sists in wiping the solder to a small fillet similar to that shown in Fig. 3. 

 The resulting joint has much less solder and therefore much less total shrink- 

 age and tendency to draw eutectic from the space between the sheath and 

 sleeve. Also, at the temperature where wiping is discontinued there is in- 

 sufficient volume of solder left by the fillet wiping technique to permit drain- 

 age drops to accumulate and fall from the bottom of the joint. Thermal 

 conduction along the sheath and sleeve cause rapid solidification of the 

 solder at the joint, eliminating the possibility of drainage. Experience has 

 shown a consistently high percentage of sound joints when fillet wiping is 



