Isinglass and Irish Moss are both fining materials, though their uses differ wildly. The principle behind both products is the same: Bonding with materials present in wort/beer to create larger masses which settle more quickly than smaller masses.
Whirlfloc - processed Irish Moss - is a kettle coagulant. It bonds with break proteins. Note kettle finings don't really work with hot break - on the contrary, they work with cold
Isinglass is most commonly used in naturally-conditioned ales, specifically cask-conditioned "real ale". Isinglass - a fish product, so vegans take note! - bonds with yeast
, causing less-flocculent cells to clump together and precipitate more quickly. It is not a multiple-use material; if the cask is roused more than, say, three times it loses its effectiveness. Warm temperatures (over, say, 70F) denature the material. When used properly, it is very, very effective. Isinglass will not remove chill haze proteins. It will only bond with yeast.
The most effective methods for reducing chill haze are procedural and ingredient-intensive. They include liquor chemistry, malt selection, mash/sparge procedure, sparge liquor pH, proper boil procedure, rapid chilling, quick separation of trub from the bitter wort, long(ish) periods of cold storage (lagering), and filtration. If you seek a product to reduce chill haze in a beer already brewed, the only thing I can recommend is Polyclar (PVPP) or Polyclar Plus (PVPP plus silica gel). The reason Isinglass will not remove chill-haze compounds (a protein-polyphenol complex) is due to the ionic charge of the two materials. Yeast and haze complexes have different charges; Isinglass targets one and PVPP the other (no, I can't remember at the moment which is which!
Short story - to reduce chill haze formation:
1. Use a well-modified, low nitrogen pale malt for the bulk of the grist.
2. Don't oversparge; polyphenol content in sparge wort rises exponentially as runoff gravity decreases.
3. Maintain a vigorous boil for at least
sixty minutes. I personally recommend 90 minutes.
4. Use a kettle coagulant like Whirlfloc.
5. Chill the bitter wort as rapidly as possible, and as soon as the wort is at pitching temperature knock the wort out into the fermenter, leaving as much break material behind in the kettle as is humanly possible.
6. Use a tank fining like Isinglass to remove yeast once the ferment is complete.
7. Cold-condition your beers - even ales - for a period of time. A week, minimum. If you still see haze, consider permitting more time "lagering". If after "long" cold-conditioning* you still see haze, consider treating the beer with Polyclar.
That's about it! Hope that helps.
* The definition of "long" is relative. For some beers/people, that's a week. For others, it's months.