It's D-Day for our Rough Scientists, who must build a furnace and bellows so they can try to smelt and form gold into souvenirs as a reminder of their six-week stay in New Zealand. To turn their powdered gold flakes into a solid nugget they have to achieve the white-hot temperature of 1943°F (1062°C) so the gold will melt.
The team has to use science to re-discover the skills of the gold prospectors from 150 years ago, who worked gold into beautiful objects on the rugged west coast of New Zealand. Will the scientists manage to make anything from the precious stash of gold that they've struggled for weeks to find? The team's scientific brains and brawn will be pushed to the limit.
Explore the science
Did the scientists succeed in getting a grip on their final challenge? How easy is it to melt and smelt a lump of gold? Mike Leahy explains how the Rough Scientists turned the gold they had collected into a souvenir from their scientific adventures in New Zealand.
You can also read about the shooting of the Rough Science series. Each of the scientists kept a diary during their time in New Zealand. Find out how they went about tackling their challenges and the highs and lows of the series.