My most popular blog entry is Tutorial: Reduce/Remove Sleeve Cap Ease. Excessive ease in set-in sleeves continues to be a source of frustration for many. Still, there are those that continue to insist that sleeve cap ease is necessary in order for a sleeve to fit over the curve of your shoulder. Another well meaning sewist claimed my tutorial only worked for children's clothing (my specialty) because children are smaller, but adults definitely need ease.
Kathleen has written a now classic blog entry, Sleeve Cap Ease is Bogus (including a sequel). She even did a series on how to draft an armhole and sleeve correctly so that no ease is needed (partially gated). It would be worth your time to go back and reread those blog entries.
This idea that ease is needed for proper fit is interesting. Unfortunately, it is a false concept. A sleeve should not fit over the curve of a shoulder. Instead, the sleeve should hang straight down from the shoulder. The shoulder seam needs to extend long enough that it reaches to the widest part or tip of the shoulder. In the picture below you can see the shape of both the shoulder and armhole. This draft will allow the sleeve to hang from the shoulder.
Instead, you will get a sleeve that looks something like this:
|Photo courtesy of Kelly Hogaboom and is licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license.|
Sleeve caps with ease amount to lazy pattern making, or at the very least pattern making without knowing better.
Children are really not much different when it comes to fit and pattern design. They do have fewer overall curves, so in many ways pattern making and fit are simpler. What curves they do have though, are smaller. Sewing a set-in sleeve in an infant sized bodice is in many ways more difficult. There is less length to work with and tighter curves. If ease is included it is just enough to allow the operator to get around that smaller circumference easier. The amount of ease is very small (1/4 to 1/2 inch) and is entirely dependent on the fabric. In many cases, it is not needed at all because the differential of a machine can be adjusted.
I can understand if this seems unbelievable. It certainly goes against the grain of conventional sewist wisdom. The best way to know, is to try it for yourself. Try using a pattern with sleeve cap ease and one without. Which sleeve is easier to sew in? Which looks better? At the end of the day, you choose which sleeve you prefer to work with.