OK, I’ll explain what I mean by that.
I’ve long been an admirer of Rembrandt’s drawings, particularly those done in reed pen, bistre ink and wash. (Bistre ink is made by boiling wood soot, often taken from wood-buring chimneys, in water. It produces as yellow-brown, transparent ink that was not favored for writing, but is well suited to drawings with washes.)
In attempting to emulate Rembrandt’s sketching methods (and those of other master ink and wash draughtsmen), I’ve even made my own reed pens (moderately successfully) and bistre ink (unsuccessfully); but eventually settled on modern tools, a steel nibbed pen like a Hunt/Speedball 108 and washes of modern sepia-colored drawing inks, or other brown or red-brown inks (as opposed to real cuttlefish sepia, which can be problematic).
So for a while I was carrying around a sketching kit of a sketchpad, pen holders and points, a bottle of ink, a bottle of wash, a watercolor brush, rinsing water and a wiping cloth. Perhaps comparable to what the old guys carried around, but more awkward than a modern portable pocket watercolor kit.
I wanted something I could stick in my pocket and have with me to sketch at a whim, without the mess and fuss, but I still wanted to sketch in brown line and wash.
After trying various tools, I settled on a couple of Sakura Pigma Micron markers with sepia colored (brown) ink in different sizes, usually 05 and 005, and a Tombow Dual Brush-Pen, “Tan”, #942 (many of the other colors in these markers are too dark to be used for washes).
The Pigma Microns are water-fast once dry, which is almost immediately. I can wash over them at will with the Tombow, which is light enough for relatively light washes, and can be built up a bit with repeated passages. The Pigma Microns can also be used over the wash which results in an interesting bit of bleed and rough line.
The result is a reasonable approximation of ink and wash, as in my drawing below (larger version here), and makes for a simple, easy to carry, no-mess sketch kit that lets me draw in ink and “wash” wherever I go (though the Tombow Brush-Pen is a bit big to casually carry in a pocket).
(BTW, I know I’ve got a lot of nerve posting one of my own drawings with a Rembrandt, but I’ve learned over time how horribly counter-productive it is to be intimidated by others’ work; so I refuse to be intimidated even by the great masters. Inspired, yes, intimidated, no.)
For a nice off-white suface, on which the brown ink lines and washes look great, I use Strathmore Series #400 sketchpads. They have a nice paper with a slight tooth that takes light washes well, and are slim enough at 24 sheets to slip into a pocket or case easily. (I also use Moleskine Cahier softbound sketchbooks, which are even thinner, about the size and appearance of a U.S. passport.)
While I’m at it, I’ll recommend a good book on pen and ink drawing: Rendering in Pen and Ink by Arthur L. Guptill and Susan E. Meyer, and a nice inexpensive book on Rembrandt’s drawings in color (which really makes a difference) is Rembrandt Drawings: 116 Masterpieces in Original Color from Dover Books.
You can also look for Rembrandt drawings in color on the terrific web site Rembrandt van Rijn: Life and Work (see my post on author Jonathan Janson, the Rembrandt site, and the related site, Essential Vermeer).
There are other variations on portable ink and wash drawing, of course; a nice fountain pen with waterproof ink and a Niji Waterbrush, in which you could carry your own mixture of wash, would be more flexible, but a bit more trouble.
I’ve been happy though, with the portability and flexibility of my “Pocket Rembrandt”, and the wonderful character halfway between drawing and painting produced when rendering with washes. If you haven’t tried it, pick up a “Pocket Rembrandt” kit and head for the marshes.
[Addendum, 11/11/2012: I’ve recently been experimenting with replacing the Tombow markers, as much as I like them, with more compact Faber-Castell Pitt artist pens (Blick link), specifically the “B” series. These are brush markers that fit more readily in a pocket than the longer Tombows.
I’m experimenting with colors like “Light Flesh” and “Sepia” to find a nice combination of two tones for my washes.]