Goldsmiths blow the outer most zone of a flame in order to melt gold or silver because the outermost zone is a zone of complete combustion, also known as luminous zone. The ignition temperature of this zone is the highest and thus helps in melting the metal the best in order to creat desired designs or patterns.

Why do goldsmiths use the outermost zone of the flame?

Answer: A goldsmith uses the outermost zone of a flame, which is non-luminous, to melt gold and silver as it is the hottest zone of the flame, having more temperature.

What does goldsmith use?

A goldsmith uses the non-luminous zone (outermost zone) of candle flame to melt gold and silver because it is the hottest part of the candle flame and has most temperature.