Three photos of the yarn I washed - to show the difference before and after.
This yarn was farm fresh and so still had a fair amount of lanolin. It smells like sheep and you can feel the lanolin. The washing had to be done so the yarn got a chance to 'bloom' - it opens it's fibers when the lanolin is removed and actually becomes bigger, fluffier and airier. If you knit it 'in the grease', you need to be prepared for the gauge, hand and drape to change when the completed project is washed.
So, in the first picture, can you tell which is the unwashed hank?
Here are a washed and an unwashed hank together.
Can you tell which is which?
This makes it a little more obvious. The inner hank is unwashed and the outer is washed. The yarn in the outer hank is a bit whiter and a bit thicker. It also has a very different drape. The inner hank - the unwashed - is a bit stiff and greasy and smells like sheep. The outer hank is fluffier, whiter, more flowing. It still smells a bit like sheep but I'm so ok with that.
Oh, in the top photo, the hank in the middle on the top is the unwashed. It's skinnier and more compact as a hank and the individual strands of yarn are skinnier and less fluffy.
In the center photo, the bottom hank is the one that has not been washed yet.