coffee staining

[tartedelune.livejournal.com]

I want to stain a pair of my jeans a darker color. I was planning on doing a coffee or tea stain, but I am not sure exactly how to go about it. I am leaning toward using coffee since it seems like it will show up more on the jeans.

Does anyone know anything about this process? Specifically I'd like to know the proper ratio of coffee to water and how long to let the pants soak (just a ballpark, since I'll be checking on them).