As they are dipping the bricks in molten gold so they look like gold bars, the soldier handling the basket for the cooling/drying process has gold all over his hands. The melting point of gold is 1,948F (1,064C) so his hands would have been severely burned after the first contact with it. In fact, any of them working near the pot of molten gold would have had to wear protective clothing and gloves to shield themselves from the heat.
UPDATE: According to the story line, the prisoners were not dipping the bricks in molten gold, they were dipping them in gold paint.
Correction: The bricks are being dipped in molten gold. When the prisoners are dipping them, Kinchloe is heard saying, "Don't get them mixed up. The bricks you dip in the gold, and the gold you dip in the red paint." Also, the bucket of red paint is obvious, but the bucket of gold is obscured by smoke. If it were just gold paint, it would not be smoking.