Measure the width of the window area.
Choose the rod for hanging the valance; typically a one-inch cafe rod is used. Measure the circumference of the rod, add 1 inch and divide by two. Record this measurement as the width of the rod pocket.
Decide the length of the valance. This is personal preference but the bubble hem works best on a valance 14 to 16 inches long. For the fabric cut length, double the length of the valance and add 5 inches plus the width of the rod pocket.
Calculate the width of the fabric required by multiplying the width of the window area by the fullness required. This can vary from a minimum of double width, best suited to crisp fabrics such as taffeta, to quadruple for softer fabric such as batiste. Add 4 inches to this calculation to determine the amount of fabric you need.
Cut the fabric to the required length and width. Join widths of fabric together as necessary.
Turn the outside edges under to form a 1-inch hem. Turn again and sew in place.
Fold the fabric lengthwise, right sides together. Align the raw edges and sew 1/2 inch from this edge.
Turn the valance right side out and press the seam only. Do not press the bottom fold.
Sew from side edge to side edge, 2 inches from the top seam. This creates a 2-inch ruffle above the rod. Sew again, parallel to this line of stitching, to create a rod pocket of the width you need.
Thread the valance onto the rod through the rod pocket and install it on the brackets. Pull the front layer away from the back layer to create the bubble effect.