Designing a graded pattern for an “FBA” or Full Bust Adjustment – Warning: This is Technical – Part 2
How is your brain capacity for grading right now? Overwhelmed yet? I wanted to break the bust grade out into a new post because its is more complicated.
Step 3: Bust and Across Back Grades
To better understand the relationship for a bust grade is different than a size grade. Looking at the quick graphic below, size grades go from one full body size to the next. The cup sizes for rtw are unrelated to the body size. For the cup size grades, you need to keep the waist and hip measurements the same for the same letter size, but the bust size changes.
I pulled my largest measurement for the cup range from my previously defined charts and dropped it into this chart.
The bust area is a tricky task to deal with. I next had to define my bust span for each size. This is the measurement from apex to apex. This part was a lot of work, so I’m not going to share this chart with you. (I know, I’m mean.) I will add this to the book I write on the subject, but at this point, I’m not going to share it. (I know, I keep saying this and it is still mean.) This part came from a lot of trial and error. I took what I knew about bra making, but also incorporating ready to wear bust spans into the mix.
For a quick reference, here is the full size chart again that I explained in the first part of this article.
My next task was to determine the across back measurement, which is the amount from armhole to armhole. I use the underbust measurement (from my sports bra chart).
In the case of the XS, the underbust was 27 on the larger side of the range. The back for each letter size is not graded for the bust, so we need to determine the back sizes before we can determine the front bust measurements. I took the 27 and divided it by 4. The quarter measurement for the XS is 6.75. These amounts are for the back of each size.
For the front, we remove the across back from the full bust measurement. This is determined by taking half the underbust measurement and subtracting it from the full bust. For the XS – A/B Cup, this leaves us with 16.5 or the half amount of 8.25.
The grade amount for each bust size going down the chart is a total of 2″ for the full grade. Each bust size is indicate by a 1″ change of circumference. This amount covers 1/4 of the body, so the grade amount shown is 1″.
Have I lost you yet?
We haven’t even gotten to actually grading yet. There is a reason it takes pattern makers years of schooling and practice to get this right.
I’m thinking I need to end this post here and let it simmer in your brain. The next and final post will be how I did the actual bust adjustments on the pattern.