I have done some seam thinking, about sewing white in general, and about the conventions of shirt-making.
These are my thoughts, and the results of my experiments:
1. First of all, unlike other fabrics your seam treatment has the risk of really showing through from the right side when you are working on these shirts. Your old 5/8" serged seam is going to look messy unless the fabric is fairly thick as well as white.
2. This means a narrow finished seam of consistent width, because any unevenness is just going to show up badly.
3. As the ultimate basic white shirts may be in your wardrobe, and therefore worn for quite a while if you avoid really dated details, they need to be fairly sturdy.
These three factors led me to one conclusion - time for flat-felled seams and time for French seams.
The question of what treatment to use brought me back to the differences between how tailors and home sewers sew - something that I read about when I did my "what's the difference between a shirt and a blouse?" research a few posts ago.
A flat felled seam is the one that is used most often in the straight seams of men's shirts.
This of course involves sewing the seam, wrong sides together, trimming one seam allowance and turning the remaining seam allowance under a bit and edge stitching it down.
This treatment lays the seam allowances on the right side of the garment. It is used in men's shirts in all seams, although I have noticed in many ready-to-wear shirts the seam where the sleeve attaches to the body is done in the reverse, where the felled seam is often made with the seam allowances on the inside, which leaves you with only one, rather than two stitching lines showing on the right side.
After much experimenting I made the front and back princess seams on my shirt with flat felled seams but decided to do them the reverse way instead, like an armhole seam. I felt with the puffed sleeves that having the bulk of the seam allowance topstitched to the right side made them too bulky and too tailored for the look of the rest of the shirt.
Here is what the seams looked like, felled, from the wrong side of the garment:
And this is what that seam looked like from the right side of the garment:
If you take your time these seams aren't hard to do, although I found with the curve over the bust I had to put aside my felling foot (something David suggests you use in his book) and do it with my own careful trimming and pressing.
This wasn't bad but really the hard part was the very even trimming and pressing.
As a result this got me to thinking about French seams which are so much easier to do, and part of the sewing vocabulary of seamstresses, women, rather than tailors.
So for my next experiment, and the shoulder seams, I sewed a French seam instead and just topstitched the edge of it down to look like a fake flat felled seam. Here is what that looked like and I would like to know if you can see the difference:
Looks pretty much the same doesn't it? The only difference was no fussy trimming ( you just have to make sure that the two seamlines you use to make the French seam, the first one with wrong sides together, and the final one with right sides together, add up to 5/8") and no fussy pressing.
And making things easier in my world means my chances of getting it right are hugely improved. I think my stitching was more accurate on the faux version.
Who says I have to sew like a man anyway to get a good strong white shirt when I can sew like a smart woman?