This sketch was done with Private Reserve Chocolat. Initially, I wasn't so crazy about this ink because so much red appeared in the wash areas. However, as I used it more, I was able to control it better, and keep the ink more to the brown tones by putting down a lot of ink and not overbrushing. Now I love this ink! It's got a deep, rich, chocolate brown color that allows for plenty of value changes. Also, in spots where there was a lot of water but not much brush action, you can see it separate into red and green. If you look at the area above the flag, you can see that happening. (You might have to click the image to enlarge it in order to see the effect.) How cool is that?!
I used a Platinum Preppy fountain pen with a .05 nib for this one. I find this fountain pen to be very fast, so it can keep up with my quick sketching and lay down plenty of ink. They only cost a few dollars, so I have a lot of them and swap them out as I work with different colors. I converted this one to an eyedropper pen so it can hold lots of ink, and I don't need a cartridge nor converter. Brian Goulet has a wonderful video showing how easy it is to do this conversion.
The Goulet Pen Company sells the O rings and silicone grease that you need in order to do the conversion, as well as the .05 Preppy pens.