Travelling light with an artist's journal

You want to do some sketching while you travel - come home with an "artist's journal". What should you take? Well, I've been refining my methods and equipment for years, seeking the ultimate solution for keeping a sketchbook and journal while I travel. Somehow I always have to keep my equipment to the absolute minimum, as I usually have to carry it on a hike and justify its presence in my baggage. Here's my latest take on what works.

Equipment and materials

New on this trip - I took an ink stick and stone, which I used, and pans of gouache, which I didn't use. The stone for grinding the ink stick is a little heavy but it's the only foolproof way I've found of carrying black ink on an airplane without getting it all over my luggage. Also, I ruined a fountain pen by taking it on an airplane with ink in it - apparently the ink seeps out through the plastic. So I don't even try to take fountain pens or ink any more. I have on previous trips taken a dip pen and bought a bottle of India ink when I arrived, but on this trip I had several plane trips so that wasn't an option.
I took water soluble pencils which I only used once but appreciated having them.
I took some black pens - Copic multiliner .01, .35 and BS. They were good on the smooth paper, not so good on rough watercolour paper. Actually I didn't really use the BS (brush) pen as I had the brush and ink.
The pencils I took were the Staedtler Mars Lumograph pencils - HB, B, 2B and 8B. Also a tortillon for smudging.
I took a white eraser and a kneadable eraser (in a little box so it didn't get dirty). And a pencil sharpener that collects the shavings.
For paints, I have found watercolour pans to be the most useful for sketching. I have a 14 colour box but I really need 16 colours. Plus a tube of white gouache. The colours I use are:
Alizerin, cadmium red, cadmium yellow, raw sienna, lemon yellow, phthalo blue (green shade), paynes grey, permanent magenta, Indian red, burnt umber, raw umber, viridian, cerulean, cobalt, ultramarine, sap green. The ones I'd leave behind if I have to are probably Paynes grey and phthalo blue. The black ink can take the place of Paynes grey for an underpainting or to add some darks but it's not always convenient to use it.
Paper - I had the local stationary store cut a few sheets of paper to A5 size and wire-bind them with cardboard covers, at a cost of about $3 per booklet. I chose some rough and some smooth watercolour paper, some cartridge paper and some plain paper. I was able to use these booklets as journals, with some pencil sketches, ink and wash, and watercolour sketches, as well as a couple of pages of notes. They only had about 6 pages each and next time I would double that. I also took a spiral bound A5 book of mixed media paper.

Methods
Usually I'm lucky to have an hour to do a sketch while I'm travelling. On this trip I had much more free time, but each sketch only took an hour or so.
For a long time I made a mess of most of my paintings because I tried to use colour when I didn't have the tones right. Finally I started doing tonal sketches, and now I sometimes do a tonal sketch first or do an underpainting using black or ultramarine and then paint the colours over it. I find the tonal sketches just as satisfying to do and extremely helpful. Also, if you're short of time, you can do a tonal sketch quickly and add some notes about colour and maybe dab some colours in the margins for reference.

Here's what you can use to do an underpainting or to do a line drawing that you can paint over with watercolour: watercolour paints (make sure they're dried completely before you add the colour layer); charcoal (not very suitable for travelling as you need to use fixative, which can't be carried easily and definitely not on an airplane); pencil; India ink; Copic multiliners; ink stick.
This painting has an underpainting done with an inkstick.

Photographs
I take a lot of photographs when I travel and on hiking trips. Usually I have very limited time for sketching and I can use my photos as an additional reference and to check details that you didn't get in the sketch. Since I'm using the photos as a reference, I often take more than one shot of the same scene, with different white balance settings (for example, when the landscape is much darker than the sky, so that I have one photo exposed to show the detail in the sky and one to show the detail in the landscape).

Back in the studio
Use your journal and photos to remind you of your trip. I download the photos to a very small laptop that I can put on my desk along with the journal and materials. Then I can look at several photos of the place or scene I want to paint, compare with any sketches I've done and then get down to painting. The photos and sketches are often a jumping off point as I may move things around or leave things out, or change the tones and hues.