HoosierBrew is Correct, you want to get the beer down to near freezing, or at the point that the haze will appear, which is protein coagulation. The gelatin will attach to them and sink to the bottom. Gelatin is the best fining agent I have tried.
When you use gelatin, does it continue to get sucked through the dip tube? Or how do you remedy using it in the keg? I’d prefer to wash and reuse yeast, but I’m interested in this too.
By the time you are using the geletin anything caught in it is something you wouldnt want in your next brew. Low floccing or mutated yeast, other types of trub etc. After primary fermentation you should get a good yeast cake, when you transfer to secondary(keg in this case) you should be leaving as much of that behind as possible. This is the yeast you would ideally repitch, not anything still in suspension.
It precipitates the yeast (and some proteins) to the bottom of the keg. When you draw the first half pint or so, you are pumping out the gelatin along with the yeast - clear sailing after.
Yes I was planning to use in secondary, but I’ve had people suggest using the gelatin before transferring off the cake. That’s why I was asking, but thanks for your comment.
Does Gelatin remove hop haze from dry-hopping? Or mainly proteins and gunk in suspension?
It will remove a fair amount of hop haze, but it comes with a price - it removes some of the hop character too. Not a big deal though - if I plan to use it in an IPA ( I usually don’t), I compensate by upping dry hop levels a bit. I mostly use gelatin for styles that absolutely need to be crystal clear though, and NOT for yeast driven styles like hefe or Belgian beers. Honestly, most of the time good pH, whirlfloc, cold crashing and conditioning get my beer plenty clear.