This is a size 32 bust so I knew it was going to require some alterations to fit my 36" bust, but because all of the shaping darts are in the waist area I knew it wouldn't require a whole lot of fiddling. After making a toile of the pattern as it was, my hunch was in fact correct. So how to alter it? I saw on Friday that Gertie did a post about resizing vintage patterns, but as you can see from the picture below I didn't want to just add width to the side seams becuase the shape is so subtle that I didn't want to loose it..so that left only one alternative..slashing! Disclaimer: I'm not claiming to be a pattern cutting expert here, but I do have some knowledge and experience, so I'll show what worked for me.
This picture is of the front and back blouse pieces that I traced from the originals. The red lines indicate where I plan to slash the pattern. I made a horizontal slash in the bust area and the vertical line will be a slash to add width to the waist measurement. The original waist was fine but a bit too tight for my liking, so I decided to add just a bit so that I could feel comfortable wearing it with lower-waisted jeans if desired.
Here are the pieces after slashing. Front:
It is probably hard to tell from the pictures what I did so I will explain as best I can!
This is typically a way to add to the bustline without adding to the waist or shoulder measurements. You make the slashes as shown, and then push the pattern outwards from the point where the 2 slashes almost meet. This makes the horizontal slash expand, which lengthens the side seams and keeps the shape in proportion with the expanding bust measurement. If you don't want to add to the wasit measurement, you simply match the slash up the bottom. If like me you want to add some width, simply spread at the bottom and set at the desired measurement. I did the horizontal slash at the underarm notch simply for reference, and made it 6cm long on both pieces. I made the vertical slash .5cm away from the end of the horizontal slash and checked to make sure it was not going through the waist darts. The vertical slash is essentially what is adding width to the bust as well as the waist. In order to do this without altering the shoulder, I cut the slash right up to the edge of the paper without actually cutting it apart. Then I adjusted the spread to add 0.8cm to the bust and 0.25 to the waist. This resulted in adding 3.2cm to the bustline and 1cm to the waist (explanation below). Note: Unless you are very confident in your skills, I recommend that you alter all pieces to the same measurements, otherwise they will not match up!
Next I traced new pattern pieces from the altered ones, and used those to cut out the fabric.
I admit that pattern cutting can be frustrating, but it is one of those things that will get easier with practice and experimentation. Don't give up if it doesn't always work, sometimes you have to go through several toiles before you get it right. And remember, a little goes a long way! Whatever measurement you add to the pattern you are really adding 4x that (left front, right front, left back, right back)..for example if you add 1cm to the wasit on the pattern you will have added 4cm to the garment (1cm x 4). Measure whenever possible, but sometimes you just have to guess (and that can often be the best way to learn)!