Why do goldsmiths use outermost flame to burn gold and silver?
A flame mainly contains three parts; the outermost part, the middle part and the innermost part. The outer part of the flame provides the maximum heat, and it produces a blue color. Goldsmiths melt gold and silver with the use of outermost part of the flame because gold and silver have a high melting point and they require a maximum amount of heat.
The outermost part of the flame contains a high amount of heat, and it also allows the particles to undergo complete combustion.