bias binder

 Dear Troy,

Since both the bias binding and the knitted fabric stretch, you need to figure out how long the binding should be for the edge you are sewing it to.

If the garment gathers by the binding, you are stretching the binding too much as you are joining it to the garment. In this case the binding will curl as well.

If the binding gathers, it means that you are stretching the edge of the garment too much as you are joining it to the binding. 

To get the right length for the bias tape, I suggest you place the bias tape flat on the table, measure and mark 20 cm on it using thread, without stretching it. Next place the garment flat on the table, measure and mark 22 cm on it the same way. Then mark the middle of the tape and the section on the garment. Next pin the ends and the mid points together, then in between. Now sew the two together and see the result. 

If you like this result, that means that you need to continue and sew the rest using the same proportions. Otherwise you need to adjust the proportions by decreasing or increasing the length of the bias tape for the same length of garment edge.

Lets say our example is the right proportion. To calculate the length of bias tape you will need to measure the edge of your garment first. Lets say it is 60 cm. We know that you need 20 cm of tape for every 22 cm of garment edge. The equation looks like this:

You can use this formula to calculate the bias tape length based on your own proportions.

Happy sewing, 

Nehzat