Adjusting a bodice pattern for cup size can be done with a slash and spread method. A larger cup requires additional length in the front bodice, but all the other edges stay the same. This added length necessitates larger darts.
The basic block presented in Patternmaking for fashion design by Helen Joseph-Armstrong has a single waist dart. The baseline draft is a B-cup. The adjustment presented is a slash to the mid-armhole from the bust point and second horizontal slash from the bust point to center front. The lower outer portion of the bodice is pivoted out from the armhole. The lower center portion is spread down so that the dart legs are equal. The cup size is determined by how far the bust point is spread: C-cup 3/8″, D-cup 3/4″, DD-cup 1″, A-cup overlap 3/8″
The front becomes longer, the dart legs become longer but the top of the pattern remains the same. The distance from shoulder seam to dart point is fixed. This really means the bust point is moving out from the body and pivoting up. As the dart increases, the shape becomes more conical and angular.
This is one way to vary cup size while keeping most measurements fixed. Another would be to keep the distance from bust point to waist fixed, or maintain the relative distance between waist and shoulder. Either of these might be a more natural trend across population. While this method would be more suited to added padding.
Leave a Reply