Solder, an alloy which is employed for uniting together two metals. The alloy is one which fuses easily, and, when fused in contact with the metals, on solidifying adheres to both, and keeps them firmly fixed. It is necessary for soldering that the metallic surfaces are perfectly clean, the quantity of solder itself required being very small. For ordinary purposes solder consists of an alloy of about equal parts of lead and tin. Fine solder contains double the quantity of tin, and coarse solder double the quantity of lead.