The most up-to-date method, and one which is being rapidly adopted by plumbers, is the use of plumber's paste. This paste when heated, forms a sort of enamel coating over the surface of the pipe. It bakes onto the pipe and does not flake off, protecting the pipe perfectly and being easily washed off when the work is complete. Only specially prepared paste will answer for this work, as common pastes will cook and flake off. The use of paste for this purpose accomplishes good results with less labor than either soil or paper. In the use of soil, it is applied before the pipe is shaved. Referring to Fig. 11, it will be seen that the soil must be applied to make a sharp line at A A, B B, C C, and around the outer curve D D, but inside these lines it may be applied without care, as these surfaces are to be shaved.
Fig. 11. - Joints Prepared with Soil, Ready to be Wiped.
The round joint, the preparation of which has been described, is now ready to be set up and wiped. A common method of holding the work in position for wiping is shown in Fig. 12. The plumber will often support his works on bricks, and hold it in position by means of them, and, indeed, many workmen prefer this method to the use of special devices for this purpose. There are many devices on the market, however, designed to hold the work in position, one of these being shown in Fig. 13. In wiping a branch joint, a third pipe holder may be used to hold the branch pipe in position. The use of the pipe holders will be clearly seen. They are driven into the work bench or into a plank, and by means of the slotted upright piece the work can be held at any height or at any desired angle. There are no bricks or other obstructions to get in the way of the workman, and there is less liability that the work may become dislodged.
Fig. 12. - A Common Method of Holding Pipes for Wiping Joints.
Fig. 13. - Use of Pipe Holders in Wiping Joints.
As already stated, it is an impossibility for the novice to learn the art of joint wiping from books. He must practice under the direction of some person who understands such work. There are certain suggestions which can be made, however, which will be of much value to the beginner. After the work has been set up, place a large piece of paper underneath it to catch the solder. The next thing is to be sure that the solder is at the right heat. A very good method of testing it, is to thrust into the molten solder a shaving or a piece of paper rolled up.
If the shaving or paper takes fire, the metal is too hot, but if the material chars quickly, the solder is right to use. Some experienced plumbers can tell the condition of the solder by holding the ladle in the solder until it is of the same temperature, and then quickly holding it to his cheek. This test, however, requires experience. When sure that the solder is at the right heat, take the ladle in the right hand and fill it about three quarters full.
Pour the solder onto the joint very lightly at first, so that it may not burn through.
Move the ladle backward and forward, pouring over the entire surface, and even out beyond the joint at either end, in order to heat the pipe thoroughly, and to a temperature of the same degree as the solder. This is a very important part of the work, cannot be hurried, and is a point not often fully appreciated by the beginner. Continue pouring, and with the catch cloth in the left hand under the joint, catch the solder as it falls off, and throw it back onto the joint.
Gradually the solder becomes soft yet firm, and when it has reached this condition, get the joint roughly into the shape required. Then, quickly laying down the ladle, take the wiping cloth in the right hand and form the joint as desired. It is almost useless to attempt to explain this last operation.
Some workmen use two wiping cloths in wiping a joint, while others use only one.
A very important point is to wipe the thin edges quickly, as the metal cools at these points almost immediately, and if this is allowed to happen, a good joint cannot be wiped. When the joint is nearly formed, attention must be given especially to the bottom of the joint. The heat of the joint will usually cause the solder to run off at this point, and the workman must with his cloth, prevent this, and prevent the joint from getting out of shape at this point. While the solder is being poured onto the joint and the latter is being brought to the right heat, the wiping cloths should be heating, so that when needed they shall not be cold.
If the solder sticks to the cloth, it shows that there is too much tin in the solder.
If there is too much tin the solder will tend to run off from the bottom and make it almost impossible to wipe a perfect joint. It is well to rub onto the cloth a little whiting or powdered chalk to prevent scratching. It is also necessary to grease the cloth with tallow, which makes it work more smoothly, and acts as a flux for the solder. Grease should also be applied to the lead work as soon as it has been shaved, in order to prevent the surfaces from oxidizing. This action takes place quickly after the lead is shaved, and prevents the proper adhesion of the solder to the lead, as it forms a thin coating between them.
Fig. 14. - Wiping of Upright Joints.
A small trowel will be found very handy for gathering up the solder that collects under the joint.