I am working a prayer shawl for my mother in Suri Merino and I fear I will not get it done in time to wash it before we leave to drive-up and see her. I will however have a 9 hr drive to finish it…so can I hand wash the hanks of yarn then let it dry and ball it and knit with it all the way to NY?
Can I pre-wash yarn?
you risk felting your yarn together if you are not careful. plus when you was after knitting a shawl it normally gets blocked to shape it.
Agreed. Why pre-wash yarn? The only reason I could conceivably think of would be for cotton that potentially shrinks.
Otherwise, just finish your project then wash and block your finished product.
It’ll be fine.
Enjoy your 9-hour drive and knit your heart out 
Dot
Plan to wash and block it after you give it to your Mom. That way she can observe how you do it and will now how to care for the shawl after you’ve gone.
Unless the shawl needs to be blocked (which obviusly you can’t do til finished) I would just let her wash it the first time it needs it. I don’t wash a finished item unless it needs to be blocked.