The other day I did some experimenting with watercolor paper and instant coffee. I had seen this used for a background for classical drawings. Now that I've tried it I can see that a bit of practice and light-handed use of coffee is a good idea. The first ones I did with just wet paper, brushed on with a big 'mop' watercolor brush, then I sprinkled INSTANT coffee crystals all over it. (No it doesn't matter if it's decaf or regular! ) I then brushed it until it colored the paper, then I re-sprinkled it with a bit of coffee. I guess I could mix some coffee up with water first to use as a tint. The one where I used bristol board I brushed with a house painters brush, it gave it interesting streaks.
The second set of papers I used two different brown watercolor paints to tint the paper. I used one big 11"x14" sheet that I taped to a board 1st. I wet it with water and the mop brush then brushed the color on. As it took on a sheen I sprinkled the coffee on and watched what it did...#1 is just coffee sprinkled and not touched, a little too heavy and spotty looking to me. #2 is same as #1 but then I brushed the coffee after awhile and re-sprinkled a tiny amount. #3 is same as #2 but I added salt and just left it alone. (note here...I just love using salt!! I love the random patterns it creates!) The sample pictures I posted here are cropped parts of the actual sheet I made. If I get a sheet I like I'll scan it, save it and perhaps I can print it out to use for drawings without worrying about messing up a hand-painted sheet. Let me know if you ever use this technique and how it worked for you. I'll be drawing with brown ink, brown pencils or pastels with some white chalk highlights on this paper. If I get time, I'll post what I do with it!