I've talked about finings tests before (at some length!) so this photo is only on here as I like the picture... plus it's a good indication of what we do to ensure the beer leaving us will clear down in cask the way most customers expect it to and thus be served reasonably clear, or at least as clear as the hop oils in suspension allow!
We use the minimum amount of finings we can get away with as they strip out flavour, mouthfeel and body from the finished beer - and anyhow, who wants fish guts dissolved in phosphoric acid in their beer? - although brewing the kind of beers we do, VERY pale and hoppy, the lower limit is a tad higher than I'd like as any clarity imperfections are very obvious in the style of beers we generally produce, meaning we must add more than I'd really like to (actually, I'd love to add zero, but the UK isn't ready for that as yet except in a very few cases)...
In the photo here you can see the finings are clumping the yeast together into floccs which are heavier than the individual yeast cells themselves and, consequently, sink to the bottom of the bottle (or cask, or keg, or silo, or whatever you put the beer in) in a matter of hours rather than the weeks it would take for the yeast to settle out under it's own violition (and it still wouldn't be totally clear after a few weeks); fining is, in essence, the process of making yeast (and protein) do what it would do in weeks in a matter of hours.
On the left we have "Mate Spawn and Die" and on the right "Dance with the Devil"; MSaD was casked up today, DwtD was transferred from fermenter to conditioning tank. We do a finings test at this point to check the protein fining in the fermenter has worked and taken out the majority of the haze causing protein which, as you can see, it has!