Bottega Veneta, AW11, Milan.

Once you have altered your basic pattern blocks to fit correctly, you will want to be able to change the design of the pattern, while remaining confident that you haven’t made any major changes to the fit of the garment. One of the first steps to understanding this process is to move the value of the dart to another area of the garment. For example you may decide that it suits your design better to have a dart running into the armhole rather than running down towards the waist.

When pattern making from previous blocks there are two methods for making an alteration to the dart, and these are also two of the main methods used for flat pattern making. The first method is called ‘Cut and Spread’ while the second is based on a ‘Pivot’ method.

The Cut and Spread method is the easiest to understand for beginners because it becomes easier to see where the dart value has gone. It is a useful process to understand because it can become more important later on when attempting more advanced changes.

Below is the basic pattern block for a female top or bodice shape with a waist dart:

Below are the instructions for how to change the bodice block from having a waist dart to having an armhole dart, such as the one in the Bottega Veneta image above:

1. First trace off a new copy of the block so as not to ruin the original block. Then draw a line from the dart notches on the waistline up to go through bust point (marked on the pattern with a dot and the initials B.P). This marks the section of the old dart which we will be getting rid of. Draw another line from bust point out towards the armhole depending on where you want the finished seam to end up. The old dart value has been marked with red lines, the new dart position has been marked with a blue line.
2. Carefully cut out the value of the old dart, and cut along the line of the new dart, making sure to leave a small amount of paper or card between the two, to keep the two pieces joined.
3. Next swing the bottom right hand corner of the pattern to close out the value of the waist dart. This will cause an open space in the position of the new dart.
4. Next tape or pin the pattern card carefully on top of a fresh piece of card. Trace around all the lines marked in red and use an awl or tracing wheel to mark the bust point. You will need to smooth out the line of the bottom hem to create a new line for the waistline. 
5. You will need to measure the new waist line and make sure it keeps the same measurement as it had on the stitching line of the original pattern. Remember to only ever compare the stitching line measurements – not the measurement of the outside edge of the pattern. You may need to alter the curve of the pattern to make the measurement the same. Trace any other stitching lines into position and other notches. Next measure the opening of the new dart and mark a halfway point.
6. Draw a dotted line from the bust point through the centre of the new dart opening. Along this line, about 1.5cm from the bust point draw a new dart point. Then draw from the dart point out to the position of the new dart arms, making sure that the original armhole measurement is kept the same as the original pattern by measuring the stitching lines of both.
7. Cut out all the outside lines except for the armhole as the dart must be folded out before the armhole line is cut.
8. Fold out the new dart by bringing the bottom dart arm up to meet the top dart arm. The folded value will sit below the dart, as indicated with a red dotted line on the drawing.
9. Once unfolded the new pattern should look like image 9 in the instructions, or the same as the image below.

Additional notes on darts:

• Always cut out the dart when folded out.
• Always fold vertical darts towards the centre front or centre back of the garment, so that the folded value is on the side of the dart seam towards the centre front or centre back.
• Always fold horizontal darts so that the folded dart value is below the line of the dart seam, or towards the hem of the garment.
• When planning dart values, make sure that the dart value is not going to cause bulk in areas of the garment by intersecting with other bulky seams or at difficult angles.
• Remember that when you change the position of a dart you are not altering the main fit of the garment, so make sure you are not accidentally shortening any stitching lines when you draw in new darts.

Catwalk image from Vogue.co.uk»

Pattern making images from The Cutting Class»