From the Dharma web site:
"• We found that this shrinks 8% in Length and 1% in Width
is a factor in planning how much fabric you need for a project. To help you, we took a 1/2 yard of every one of our fabrics, measured the length and width, washed it in a machine with very hot water, dried it in a dryer set on very hot setting, and then measured it again.
Then we calculated the % shrinkage in length and width which we are reporting to you.
Please be absolutely clear!
We think it's the worst case scenario.
This is only our experience and yours will vary.
Please do not take this as some sort of guarantee about how much the fabric will or will not shrink in your circumstances.
Most fabric shrinks when washed and dried, especially undyed fabrics such as the ones that Dharma sells. Fabrics that go through a dyeing process will also go through a shrinkage process. Dyed fabrics that you would normally purchase in a fabric store have already gone through a dyeing process and therefore have gone through a preliminary shrinkage process. So when you buy undyed fabric from Dharma, you're buying fabric that has never been shrunk."
I run the seam lengthwise on wings to get the silk as tight as possible.
This orientates the grain spanwise not chordwise.
If the grain is run front to rear, chordwise, the silk will sag between the ribs of open structures, because it won't shrink enough to prevent the sag.
Don't ask me how I know.
You do have to stretch the silk while wet
to get it to shrink properly.
Don't rely on just the shrinkage of dope to get the covering tight.