HOW TO GRADE A SEAM
Bulk occurs when stitching several layers of fabric together, which can result in unattractive seams. You can reduce bulk by trimming the seam allowance to different widths. This is called grading.
Seams that will be pressed to one side or enclosed such as those on collars, facings and linings, should be graded to lay smooth and flat.
In the example below I'll show how to grade a seam that will be pressed to one side.
First I stitched two fabric pieces together using a standard 5/8" seam allowance. Then I trimmed the seam allowance (the one on the very top layer) down to 1/4" and I left the other at 5/8"
Then, I opened the fabric and pressed the seam (closed) to the left side.
If for example you are grading three layers of fabric, I would trim the 1st layer down to 1/4", 2nd layer 3/8" and leave the 3rd layer at 5/8".
For four layers of fabric, I would trim the 1st layer down to 1/4", 2nd layer 3/8", 3rd layer 1/2" and leave the 4th layer at 5/8".
If the seam is to be enclosed (depending on how many layers of fabric of course), I would trim the 1st layer down to 1/8", 2nd layer 1/4", 3rd layer 3/8" and 4th layer 1/2".
Pretty easy right?! Try grading the seam allowances on your next sewing project and check out how much it reduces the bulk.
Do you grade your seam allowances? Do you do it a little differently than I do? Please share with us in the comment section.