By Friday afternoon, the mood on commodity trading desks changes.

For the first four days of the week, traders have been trying to profit from their bets. By lunch on Friday, however, they’re thinking about how much risk they can tolerate until markets reopen on Sunday evening.

Anything could happen while markets are closed: news of a new war, an election result, an unexpected OPEC announcement or, as seen recently, a market-moving presidential post. Forty-eight hours can be a long time when traders are holding a position tied to a few of the world’s most actively traded markets, and there’s nothing they can do until trading resumes.

“From about lunchtime, the desk basically stops thinking about making money and starts thinking about what…