Adam savage from that TV show - doing “real world” weathering:
[Y] Love his work!
Definitely a fun and informative vid., the secret weathering weapon was indeed a surprise, thanks for sharing the link.
Regards, Peter
I had the idea to use coffee as a weathering agent and gave it a try last year. I thought it might be an alternative to alcohol/India ink. Didn’t do much for plastic structures or rolling stock. The coffee just shed right off without any noticeable discoloring. I think it might work better on wood structures as they are more porous and would stain more readily. I have a few to build this fall/winter so maybe I’ll give it another try. Don’t have time right now to watch the whole video but I’ll look at it later and maybe pick up a few tips.
Club I used to belong to before moving, experimented using Coffee to paint rocks. If you needed a nice sandy color, then cold coffee worked fine. 
The one line that caught my eye was when he said " use a multitude of colours, for a better dynamic". When I went to many different online sights on “how to paint the Rockey Mountains” every artist said to use many, many colours. One even suggested you have at least fifty colours for a good job.[:S]
I went to walmart and I think I bought about 18 different colours of their $2.00 craft paint and was really pleased with my first attempt.
Now that I hadn’t thought of but sounds like a good idea. I’ll have to give that a try.
I have my cup of coffee here but haven’t watched the video yet. But as it happens, I will be needing to model sandstone - i.e. Ruby Canyon in western CO - eastern Utah so I wonder if it would work for that. I’ve noticed the sandstones are really pretty there with orange, reddish, purplish as well as buff, hues.