Question about Alchemy (astral)

Hello everyone, i just got a question.
I got a +11 bow now, no ADV used. I would like to try to make it +12.
Does astral means, that if it fails to +12, it will still be +11?

Thanks in advance

unfortunately not.
it'll go back to +4, and maybe even get damaged, as immortal is only to protect your item from getting completely destroyed (yet, as i mentioned, it can get a repair invalid).