Despite it’s fine appearance Liberty Tana Lawn is very hard wearing. I still wear skirts that my Granny wore in the seventies!
I don’t prewash my fabric before I use it for my sewing projects. Because it is such a high quality fabric the shrinkage is negligible.
Wash at 30 degrees (although I bung mine in at 40 with my normal wash and it’s fine). To keep it looking it’s best use a laundry powder or liquid that doesn’t contain bleach.