Setting the seam
Why do we "set" seams when we are quilting?
The simple answer is that we get a better, more accurate seam.
For those unfamiliar with the term, 'setting a seam' is when you press your freshly sewn seam flat before opening it. Once it is 'set' then you open the unit and press the seam allowance either to one side or open.
This initial pressing melds the thread into the fabric, kind of flattening it. Theoretically it then takes up less space in the seam allowance. This should lead to more accurate piecing.
And in my experience, it does!
I always press my pieces flat first and then decide how I will press the seam allowances. It's a good habit to get into from the start.
Thank you for your question.