I taught myself how to sew from commercial patterns, and then from self-made patterns that imitated the model of the commercial pattern. When I started taking classes in my university’s theatre department, it was from a desire to learn how to do things differently, more efficiently, and more accurately, not to learn how to do them in the first place (needless to say, I didn’t see myself continuing as far as tailoring at the time).
And I embraced everything I was taught immediately, except for one thing: I held onto the method of including seam allowance in patterns for cosplay. I understood why it made sense for theatre, but I figured that since I was only making the pattern for myself, I could keep doing that much my old way.
So I noticed when I drafted my last pattern and I didn’t include seam allowance. But I didn’t miss it. Even though it takes longer to add the seam allowance—granted, by about two minutes per piece with a decent $6 transparent ruler—having the seam allowances marked instead of just assumed makes it easier, for me, for the garment to fit exactly as the pattern intends. It also helps with pattern matching (something pretty important for Kuroshitsuji, amongst hundreds of other cosplay), since I can immediately distinguish which sections of the fabric will end up visible and which will be pressed and trimmed out of sight.
And when it’s four in the morning before a convention, it’s way easier to pin and sew a straight line when there’s a marked seam allowance telling me exactly where I need to stitch, without having to strain my eyes at those 1/8” notches on the machine.