As an urban sketcher I carry my sketchbook al the time with me. There is space in my bag for two sketchbooks I usually carry an Alpha and a Beta Sketchbook from Stillman & Birn. Although their sketchbooks accept a lot of water, is the Beta the one recommended for wet media. It is a wonderful watercolor paper. Extra white as I like it. As you see in the below image, the ``sketch`` is in all aspects a finished watercolor. The brilliant glowing colors were achieved by glazing a translucent pink red over a yellow. The darker color was added later. So at the end this is a painting with just 3 colors.
Trying things in your sketchbooks on site give you the option of experimenting. I was sketching with Luis Simoes (who is travelling and sketching around the world) at Alexander Platz and he wanted to know all about watercolors. I told him that sometime before going out to sketch, I prepare some pages with some glazes (that is not something you can not do always on site, because you have to wait that the first colors dry before putting the second glaze and this took time). I painted a short strip to show him the principle and then I keep drawing. I left a wide empty strip of white paper over it that worked very well with the white pavement. In the the final watercolor I decided that it work well as a snow landscape.
I try to work only with formats for which I know I will find an affordable frame and passepartout, like Ikea frames. I will cover the border of the paper with masking tape. The Masking tape will damage the structure of the paiper, but I don`t care much, since normally what artist will do is to cut out the area outside the passepartout. On the other hand the white border makes the painting more elegant (it looks as it is a print)
This is the final result. I added some snow flakes with white acrylic color. The painting is 40 x 50 cm on Boesner 300 gsm watercolor paper.
PS: People keep asking me where I can find Stillman & Birn sketchbooks in Germany. Well, I finally found a place in Berlin: Künstlermagazine in Prenzlauer Berg. They also sell it online so you would get it all over Germany.