Wood staining technique question

As I am not a RR guy I needed to come to the source of RR know how. So Here I am.

Holiday greeting not my model train brethren.

Many moons ago a RR guy told me a way to stain wood for a brown weathered or creosote look. The wood was placed in a liquid with some steel wool. Worked great. Can’t for the life of me remember what the “liquid” was.