Series 4, Take 6
"These are the blood tests. We're trying to get the right color blood," says Burum. "If you have somebody who's wearing a light outfit, you usually use a little darker blood. If somebody's wearing a dark outfit, you use a little lighter blood so it shows up better. Otherwise, it just kind of goes black. This is if somebody's been shot and you want it to read red, so it depends on the background."

He says there are about four or five versions of blood. "Blood is typically made out of some sort of base like Karo syrup, then the color is put into it. And it's usually scented, so it smells nice. The old Max Factor used to smell like rose petals."