First, you’ll need to determine the amount to add to your back bodice. On your muslin, slash two vertical lines where your shoulder blades are. Then ask someone to measure the opening of these slashes when you stand straight, in a natural posture, arms slightly toward the front. Now time to adjust the pattern!
Start by tracing your bodice back piece.
Draw a vertical line starting at the shoulder and extending a little below the armhole, then connect the bottom of this line to the side of the bodice, parallel to the shoulder slope. The exact positions of these lines doesn’t matter, as long as they don’t overlap with a bodice dart.
Cut the piece along these lines, then slide the armhole part along the shoulder slope until you reach the desired width.
Redraw the shoulder line and the side line. If you broadened the back by less than 1 cm (3/8”), you can simply ease the back shoulder with a basting thread to make it fit the front shoulder. If your adjustment was bigger, then you’ll need to add a back shoulder dart.
Draw a line perpendicular to the shoulder slope, that meets the tip of the waist dart if it exists (if the bodice does not have a waist dart, position the line in the center of the shoulder).
Starting at the shoulder, draw a new dart, with the distance between the legs equal to your adjustment value, and the apex situated between 6 to 9 cm (2 1/4” to 3 1/2”) from the shoulder. For instance, if you’re widening your back piece by 2 cm, the legs of the dart need to be 1 cm away on each side of your reference line (so the total distance will be 2 cm), and meet on the reference line 6 to 9 cm from the shoulder (the larger the dart intake, the longer it should be).
Your back bodice is ready! We recommend sewing another muslin to check the fit and balance of the bodice before making the final garment.
The adjustment is exactly the same on grown-on sleeves bodices such as Mélilot! Cut along a line similar to the one above, making sure to go past the sleeve.