I use Winsor & Newton watercolors and gouache paints, which comes in a tube. Typically I can keep the watercolor paints on my palette for several weeks. I used a large plastic 12″ x 15″ tray with individual cups around the outside with a large area inside the tray to mix your paints. It came with a lid, which was nice because it helped to prevent your paints from drying out so quickly.
If I knew I wouldn’t be able to get back to my painting for more than a few days, I would cover the plastic tray in plastic wrap and then put the lid overtop of the tray. This method gave me a couple of extra days, maybe a week or so, before my paints dried out completely. While it is true that all you have to do is add water to revive your dried up watercolor paints, it is better to keep the paints wet.
If the paint dries out completely and you go back to add water it will often times be gritty and is difficult and if not impossible to get rid of that graininess. When using grainy watercolors, that beautiful wash of blue you just laid down on your watercolor paper will have these tiny specks of dried paint here and there that can be very distracting, ruining your serene sky. (I have made this mistake in the past, only to have to redo the whole thing once again!)
A few years ago I started to use paint trays that come with individual cups with tight fitting lids. Even though the mixing area is smaller than my old tray, I’ve found this type of tray really suits my way of working. Ninety percent of my paintings are smaller than 9″ x 12″ so I don’t require huge areas to mix up my washes.
These paint trays solve my problem with the paints drying out too quickly. Since they have individual cups, even if one color dries out or your cadmium yellow accidentally got alizarin crimson mixed into it, you can easily and quickly change out one cup of color — wash it out, refill it and you are good to go!
Every now and then I still like to completely wash out all of my paint cups and paint trays. I especially like to do this before beginning a large project or series of projects — it is part of my ritual, a fresh start.
As I clean off my drawing table, organize pencils, brushes, papers, gather reference material, and sketches, I am also thinking about this new project. At this stage, the sketches are already completed and finalized so I am beginning to think, what will I work on first? What colors will I use? Should I do a color study first? How detailed will the picture be?
Once my desk is cleaned off and organized, my paint trays are washed out and cleaned, it is time to add the paints. I always putting the paints in the same place in the same order. Being consistent with the placement of the paints in the tray is very helpful. For example, when I want to mix up a yellowish green, I immediately know which container holds my new gamboge, cadmium yellow and spectrum yellow, creating an easy method of mixing the color I want to use.
Using good tools, organization, simplifying your process, and creating a consistent set up with your paints will help you be more efficient in your work.