White flowers are always a huge challenge for botanical artists. I find that many painters use grey and the flowers look muddy. I took a class with Margaret Saul on painting white flowers and she recommended that you mix red, yellow and blue to create greys. You can create greys that have pink, lavender and green shades. This is great advice so that all the shadows are subtle shades of muted pastels. I find that this works well. In conjunction with using this technique I also experimented with something on my own. I went to my local Home Depot and went to the paint department. They have all the paint chips from the manufacturers for free. I took as many as I could without looking like a kleptomaniac, and they were all shades of white. It is amazing how many different shades of white there are! I then took my watercolor paper and punched a hole with a hole punch and placed it over the paint chips to decide which "tint" of white I wanted to use. Here is a break down of what I did:
1. Use masking fluid to completely cover the white flowers. Leave the stems and leaves alone and let the masking fluid dry completely.
2. Test out colors. Let them dry. Watercolor usually dries a bit darker. You want the color to hardly be noticeable.
3. Mix up enough color to paint the entire sheet of watercolor paper. (use lots of water and thoroughly mix)
4. Wet the watercolor paper with a big flat brush. Let the water soak in but the surface should shimmer. I use 300lb paper so it is not necessary to tape it down. If you are using thinner paper you will need to tape it down.
5. Apply the pale watercolor wash as evenly as possible to the entire area, work horizontally. Let it dry.
6. If the tint is too light re-wet and apply a second layer, this time vertically.
7. When paper is dry remove the masking fluid. Don't leave the masking fluid on for more than 24 hours. You now have a slightly tinted background color which makes the white of the paper whiter and brighter. It helps to make the whites crisp and clean and the background still looks white.
Try it out and let me know how it works for you!