Teehee, forgive the exuberant title, but still.
I just did my first FBA!
Another technique for my sewing and dressmaking toolkit. Utterly delighted that it worked. Well, actually, I don't know for certain that it worked but I did hold the edges of all the relevant pieces against each other and I think I made the adjustments where needed.
So, FBA. What is it?
FBA is short for Full Bust Adjustment. Commercial patterns are made for women up to B cup size but they don't work great for anyone with a bit more up top.
So a full bust adjustment allows for both more width across the body as well as more length in the other dimension.
Here's a photo of one of my cut up and reassembled pattern piece, the upper front:
The technique involves finding the bust apex (the blue cross a little below the original bust point that looks like a cross hair symbol), cutting to it from the hem parallel to the grain line. Continuing the cut towards the arm hole, I picked the sewing mark to cut towards - but stopping short at the seam allowance.
This last bit then acts as a hinge that keeps the pieces together. [**] Then cut from the side seam towards the bust point but leave a hinge at that point (the apex).
You then pull the lower piece (the one nearer the side seam) away from the other main piece keeping the vertical edges parallel (those running from the apex down to the hem): move them right and left apart from each other by the measure that the pattern piece was too short by.
Put a strip of tissue paper underneath and tape down. (I did this in two steps: I taped one edge onto the tissue strip, then I marked the width where the other edge needs to be, drew a line down and then taped the other edge down up to that drawn line. It can get quite fiddly)
Now you can then move the dart back to where it was. The dart is just a bit wider than before to create a more rounded shape and larger cup size over the bust.
I checked the side seam against the front side seam and found that the above dart I drew in the thick blue line was a bit too deep, so I decreased this by a good centimeter in total.
You also need to adjust your piece that's closer to the front centre. Here that wasn't a problem because this piece ended in a point so I didn't strictly need to move the central piece down to come to the same hemline.
I also checked the lower front piece and the contrast fabric piece against all the new seamlines and extended them.
I had a bit of a hairy moment when the lower front did not seem to be wide enough at all. It turned out that I forgot that both upper front pieces need to be sewn together first and the combined width would therefore lose the two seam allowances of the separate pieces. Makes sense once you think of it. Uh.
All's well that ends well.
Now I just have to cut out some fabric to see if the adjustment really worked. I might go the muslin route before I cut into my expensive wool fabric!
**Correction: I listed two steps in the wrong order before. Apologies, I now corrected this.