you're finished vs. you finish


I have some questions on the sentences below:

  1. Will that be a sweater when you’re finished knitting it?
  2. Will that be a sweater when you finish knitting it?
  1. I think both sentences are right. However, I don’t know why 1) uses “be finished” there. Is there a nuance difference? Or, is 1) just wrong? Please let me know!

Thanks in advance,

The first is less formal and can most often be heard in speech. Grammatically it should be “… when you’ve finished knitting it”