While writing historical fiction, you need to do two types of research: soft and hard. David Mitchell explains
The hard research involved going through archives and finding items such as the journals kept by the employees of the Dutch East India Company. It also involved seeking out history professors and persuading them to — as Mitchell describes it — “spend a couple of hours answering my rather undergraduate-level questions.”
Meanwhile, the soft research was something that continued until the day Mitchell finished his manuscript. While writing a scene in which a character was shaving, suddenly Mitchell needed to know: Did they have shaving cream in those days? Would it have been affordable to a middle-ranking clerk? Or in a scene at night: How would the room have been lit? By candle? Or by oil lantern?
“You have to know all of that,” Mitchell says. “Sometimes you can’t finish a sentence without spending half a morning going away and finding it out.”
While it was important to understand the intricacies of 18th century life, Mitchell says he also had to be careful to “hide” this knowledge so that it wouldn’t be a distraction: “Otherwise you get ridiculous sentences where the servant walks in and says, ‘Is it going to be the pig tallow candles, my Lord, or would you prefer the sperm whale oil lantern?’ ” [How David Mitchell Brings Historical Fiction To Life]