I have a separate book for testing the tools of my trade. Pencils, pens, inks and watercolours all get their first try-out here, and I can refer to this book when I am searching for just the right implement amongst the vast array of choices in the chaos of my crazy room.
On the rare occasion I forget to drink all my morning coffee, even the delicious drops become an experiment in colour:
So far, not enough dregs have remained to tint even a postcard. Yes, that is how good my coffee is.