Although the flame temperature of the spray gun can reach 1500℃, the melting point of platinum at high temperature is 1769℃. Therefore, even if the spray gun continues to heat, platinum will not melt.

When the flame of the spray gun contacts with platinum, it may not be enough to completely cover the surface of platinum, resulting in uneven heating and unable to effectively melt platinum. Platinum is easily oxidized at high temperature, and the resulting oxide layer may prevent further heating and melting.