Things You'll Need
2 pieces of wide fabric
Tape measure or yard stick
Water-soluble fabric marker
Baffle-box comforters, whether filled with down feathers, cotton filling or a poly-cotton-blend stuffing, are unique from other comforters as the filling material is sectioned off into individual chambers. The individual chambers work to keep cold areas of the comforter from forming as the filling settles and shifts over time. To sew a baffle-box comforter, you only need two large pieces of fabric and the filling material of your choice.
Add 20 inches to the length and width of your mattress (see Tips for mattress measurements). Purchase and cut two pieces of fabric to this size, utilizing the highest-quality wide muslin or quilt-backing fabric available, both of which generally run 110 inches wide.
Fold one length-side of each piece of fabric to the back by a ½ inch. Pin the fold and sew a ¼-inch-wide seam along that one side of each sheet of fabric.
Spread one of the fabrics out on a flat surface, with the pattern or front of the fabric facing up. Mark a 1-by-1-foot grid over the face of the fabric, using a tape measure and water-soluble fabric marker to form horizontal and vertical lines.
Layer the other piece of fabric over the grid-marked fabric with the two hemmed sides resting over one another, and the patterned sides facing in. Align and pin around all four edges. Sew a ½-inch-wide seam along the three sides that are not hemmed.
Turn the material right-side out and pin the fabric together along the grid lines that mark the width of the fabric. The width lines run from the open, hemmed length side to the opposite length side. Sew along each width line, removing the pins as you go, to form parallel channels between the layers of fabric.
Stuff the individual channels with your filling material as full as you want them to be. Distribute the filling evenly along the entire length of each channel. Pin the open side of the comforter closed once you are certain of the fullness and thickness of the bedding and don't want to add anymore. Sew the open side closed with a ¼-inch stitch over the existing stitch lines.
Sew across each of the length grid lines to close off individual boxes of the comforter, locking the filling into place. Fill a spray bottle with water. Mist the surface of the top fabric to wet the grid lines and make them disappear. Don't soak the comforter. Wet the lines again where marker reappears after drying.
Twin mattresses measure 39 by 75 inches; full or double beds measure 53 by 74 inches. Queen beds measure 60 by 80 inches, while king beds measure 76 by 80 inches. The amount of filling you need will vary depending on the size of your comforter and desired fullness. Narrow 40- to 44-inch-wide fabrics can be used for this project if you sew long panels of the fabric together to form one piece, used as the top or bottom of the comforter.