Start by drafting a design on paper. Since it's values that are important and not colors, you can use a pencil on graph paper. Make some areas dark, light, and medium in value. Figure out how many squares you'll need of each. Traditionally watercolor quilts are made of 2" x 2" squares. When sewn together with a 1/4" seam allowance, the final size of each square will be 1.5" x 1.5".
Step 2 - Sorting
Organize your 2" x 2" squares into three piles: dark, medium and light. Darks usually have a background that is black or a very dark color with foreground colors that are very vivid and bold. Lights usually have a white or very light colored background with foreground colors that are pastel or muted. Sometimes it helps to have a "medium-dark" and "medium-light" pile.
Organize your 2" x 2" squares into three piles: dark, medium and light. Darks usually have a background that is black or a very dark color with foreground colors that are very vivid and bold. Lights usually have a white or very light colored background with foreground colors that are pastel or muted. Sometimes it helps to have a "medium-dark" and "medium-light" pile.
Step 4 - Finishing
Piece together, quilt and bind.
Resources If you don't have lots of brightly colored floral fabrics, you can buy a set of 200 pre-cut 2" x 2" squares. You can also buy them in strips and fat quarters. A handy tool for making watercolor quilts using 2" squares is "Quilt Fuse," a fusbible webbing that has a 2" x 2" grid marked on it. Arrange your fabric on the Quilt Fuse using the grid, fuse them in place with an iron, then fold the rows over and sew a whole row at one time.
Here are some watercolor quilts that I designed and made: Watercolor Sunset, and Watercolor Swirl.
If you've made a watercolor quilt, please post a link to a photo of it in the comments section.