Quote Originally Posted by IUFG View Post
I believe a lot of brewers use isinglass as a processing aid.

Not sure about Guinness. That may piss on the chips of a few vegan/veggie beer drinkers..
It's used as finings to clarify the brew. I used it just the other day for my weird rhubarb mixture.

Talking of which, I used a hydrometer the other day to test its specific gravity and it has a whopping alcohol content of about 3%.