Shadowing occurs in a quilt when a darker fabric shows through a lighter fabric. It is particularly an issue with turned-edge appliqué because the seam allowance creates an edge that is visibly lighter than the rest of the patch.
To prevent this, add a lining of plain white fabric to the back of light-colored appliqué patches. Mark the shape on the right side of the appliqué fabric and cut out with a seam allowance. Mark the same shape on the lining fabric and cut without a seam allowance. The marking lines tend to be visible on the back side of the appliqué fabric so use them as a guide to position the lining shape. Apply water-soluble glue to secure the lining to the back of the appliqué.
The patch is now ready to be needle-turn appliquéd. The seam allowance will be turned behind the lining fabric, reducing or eliminating any shadowing.
Unfortunately, not completely. The interfacing is somewhat translucent and some shadowing will still occur.
So what is the solution? One option is to use two layers of Apliquick interfacing, carefully fusing the second layer over the first layer on the back of the appliqué fabric.
Two layers of interfacing will make your appliqué a bit stiff, so another option is to use a plain white fabric lining in addition to the Apliquick interfacing. The interfacing is fused and the white fabric is glued to the back side of the appliqué fabric. It doesn’t matter visually in which order they are applied, but in testing I preferred using the white lining first and the interfacing second. The interfacing has a denser, smoother finish which makes it easier to turn the seam allowance with the Apliquick rods.
There are still two layers with this approach but the lining layer doesn’t add as much stiffness as two interfacing layers. A third approach is to apply the white lining to the back of the appliqué fabric and only a narrow outer ring of Apliquick interfacing.
The appliqué will feel softer and only a bit of shadowing is evident.
Here is a side-by-side comparison of the sample photos.
The choice is yours, and you may have to do your own tests with the fabrics you are using. One way or another, lining your appliqué patches is the surest way to avoid shadowing.