"Work into" is correct. " During WWII we used to work the food coloring into the margarine, which was white during those days. It was a lot of work!
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
AnonymousWhich should I use in the following passage?I'd say it's your choice. I find both of them acceptable. I would probably use "into" as one word, though I understand your reasoning concerning the two-word form.