Shaping the underbust

I didn’t really know how to title this post but I did want to revisit the subject of princess line side panel shaping (from Lazy pattern making) as some of the comments from visitors regarding bust shaping were interesting.

Regarding the development of a snug fitting bodice shell, in the Apparel Manufacturing Handbook, Solinger provides this sketch:

With regards to draft development, he states (pp 74-75):

…for an apparel form with a pronounced bust cleft and under bust line, must have a triple angled dart with a waist line base and an angled center front or dart in the center front (see Fig. 3-20).

[Ha! I also said the center front line is curved] Solinger continues:

The center front angle or dart is located at the cleft point. This can be proven by generating the surface with a straight edge. The generation of the surface, a combination of rotation and axial movement, will show that although this sloper can be drafted by a combination of Cartesian coordinates and triangulation, it is drafted with best precision by complete triangulation.


Which leads me to comment, have any of you drafted via triangulation? Solinger (below) provides these sample sketches as an example of the difference between the two methods. Having done both, I find best results are obtained via triangulation.


Referring again to the sketch in figure 3-20, see the curvature of the underbust? I have rendered similar drafts. Regarding the shaping of the princess line, I have found that better fit results are obtained if one plies more effort towards shaping the under bust (of the side panel of a princess line) rather than the focusing on bust prominence which is what seems to get all of the attention in pattern drafting books. Shaping the underbust can be a tricky affair. Consider the variety of bust shaping which Solinger defines these with this sketch (Fig 3-23a, Fig 3-23b):

Solinger further elaborates with another sketch (Fig 3-24), the discriminating feature between the two being that the one below is described as “profiles of basic bust surface shapes” while the one above is described as “profiles of natural bust shapes”.

He describes the differences thusly:

Bust shape also varies with respect to surface perimeter as well as bust profile. Fig 3-24 shows profiles of five basic bust surface shapes; conic, parabolic, hemispheric, [sic] parabolic, droop, conic droop. In the parabolic droop, the nipple is on the horizontal of the underbust point. In the conic droop, the nipple sags below the underbust point and therefore the bust droop is greater than in the parabolic droop.

Be that as it may, I don’t understand the difference between “profiles of natural bust shapes” (3-23a) and “profiles of basic bust surface shapes” (3-24). Maybe one of you better versed in geometry can explain the difference to me.

In response to a question that Shannon asked me, as to which measure -the under bust or over bust- should be weighted more heavily in the development of bust shaping in a bodice draft, Solinger (author of the bible of apparel manufacturing) wrote:

The larger the bust cup, the greater the distance from the nipple to the underbust girth, and greater the projection from the torso (on a line perpendicular from the nipple to the torso’s vertical).

Being that the value of the underbust deserves greater prominence, I’ve always felt the underbust was the better of the two and for two reasons. One, you can’t take that measure on a horizontal plane -measuring under the arms but above the bust- and that’s how the measure will be applied in a draft because nearly all drafts are cartesian rather than triangulated. Secondly, if you’re large busted, the measure will not reflect the dimensions of the rib cage because one has varying amounts of breast tissue up there. Using the under bust measure is best because it’s a standard that can be applied in all cases, regardless of bust fullness.

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4 comments

  1. Beverly says:

    I believe the drawings in 3-23a represent the profiles of the cup sizes we use such as AA, A, B etc. and in 23b, those same breasts in an uplifted position, which would be the goal of any bra-maker worth her salt. :)

    However, the profiles shown in 3-24 are the profiles (amount of sag if you like) that could occur in ANY size breast; for example, the conic droop could happen even with a B cup, and I have seen many DD natural breasts(not augmented, lifted or otherwise “encouraged” through surgery) that are the “hemispheric” profile. Lucky women!

    Certainly the profile of the breast is affected by pregnancy, illness, weight loss or gain, the ravages of time and gravity, and the individual’s diet choices. If you eat a lot of (non-organic)chicken for example, you may be storing those hormones in the fatty tissue of your breasts. Think about it – there is a reason chickens grow to maturity in six weeks.

    Genetics are also a huge determiner of how perky a woman stays over her lifetime. Want to know how you might look at 65? Just check out your mother.

    Bra-makers, especially ones that work with stretch fabrics, know that the amount of uplift a bra can provide is easily manipulated by what amounts to straightening the underbust dart. if you allow more space from the apex to the wire line,(in other words, if the dart is curved like 3-20 or greater) the breast will tend to sag more. Staighten the line somewhat, and the bottom of the breast is thrust upward.

  2. J C Sprowls says:

    I had no idea there was a manual method of drafting by triangulation. I presumed the geometric surface measurements laid in the realm of software. Would you please recommend several references on the topic?

  3. Sarah Smith says:

    I don’t understand the difference between “profiles of natural bust shapes” (3-23a) and “profiles of basic bust surface shapes” (3-24).
    “and greater the projection from the torso (on a line perpendicular from the nipple to the torso’s vertical).”

    —in Fig.3.23, this measurement increases with each bust size, and in Fig. 3.24, it’s the same for each bust. But I have no idea why…I’m not much of a mathmetician.

  4. Andrea says:

    I don’t understand the difference between “profiles of natural bust shapes” (3-23a) and “profiles of basic bust surface shapes” (3-24).

    The first diagram compares the shape as the SIZE changes–from smaller to larger. The second diagram compares same size breasts (image they are all Cs), according to their shape.

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