A bishop (or "bishop's") sleeve is a classic look, but it's not boring. It's the difference between a basic blouse with a slightly full sleeve, and a blouse with a beautifully draped sleeve that's fluid and fabulous.
Even the most basic blouse moves up from a utilitarian, "wear for work" garment to an elegant dinner blouse - worn with a satin or velvet skirt, it will even take you to a holiday party!
The fullness in this sleeve is entirely at the cuff; there is virtually nothing added to the sleeve cap. This is not a "puffy" sleeve.
It's not hard to draft, but there's a bit more math involved than in some sleeve designs.
You'll start with the sleeve from your basic blouse, a straight sleeve with no elbow dart.
Divide the sleeve into four approximately equal sections - draw vertical lines from the cap to the hem and cut along those lines. Do not cut through the cap - keep the sections connected just a tiny bit, if possible. (It's not really a problem if you cut them apart, it just makes it a bit more difficult to keep them in order and make them meet at the cap properly)
Spread the sections apart to create the full shape of the blouse. I spread 2" at the hem - you may find that you like more or less fullness, and it can vary depending on the fabric you're using.
In addition to spreading the sections, you'll need to add a little length to the back part of the sleeve only. This creates that beautiful drape that is what the bishop's sleeve is all about.
Draw a short line 3/4" below section #3 - this is the section next to the center, but towards the back of the sleeve (remember, the back of the sleeve is the side that has 2 notches in the cap).
Now, draw the new bottom edge. Draw a nice curve from side to side, incorporating the lower area towards the back. This might take a bit of practice, but you can do this free-form if you'd like.
Your final design will look something like the one at right.
You'll need a cuff to gather and hold the fullness at the wrist. The measurements in the illustration are just guidelines - you may need to adjust depending on the size of your wrist and how deep you want your cuff to be.
This cuff will finish at about 1 3/4"; you may opt for a more narrow cuff and let the sleeve drape take the focus, or you could go with a higher cuff with more buttons or trim.
You'll also need a vent to allow the cuff to open properly. The vent is just a short line drawn in the longer area - see the illustration for size and placement.
The vent can be finished with a narrow binding or a placket. The binding is probably easier, and still looks very nice.
Decide how you'd like to use the bishop - on a dress or top - and the neckline you'd like to use. In this case, I'd keep the focus on the sleeve, so a simple neckline compliments the sleeve nicely.
And remember to add seam allowances and a hem before finishing your pattern!