Isinglass is a form of gelatin that's seldom seen on supermarket shelves. It is derived from the air bladders, or sounds, of various commercially-harvested species of fish. It can be used in the same ways as other forms of gelatin, but in practice its primary use is as a fining, or clarifying agent in beer making. The natural sediment in beer will settle out over time, but isinglass speeds the process and makes an attractively clear brew. There are several alternatives to isinglass, added to the boiling wort or in the fermenter before bottling.
Precipitate proteins from the wort by adding 1 tsp of Irish moss for each five gallons of wort. Irish moss is a seaweed containing a gelling agent, called carageenan, that is widely used to thicken chocolate milk and ice cream.
Add Whirlfloc tablets, rather than powdered Irish moss, to achieve the same clarification. Whirlfloc tablets are Irish moss with added carageenan, compressed into tablet form. One tablet will clarify five gallons of wort.
Use either Irish moss or Whirlfloc tablets by adding them during the last 10 to 15 minutes of boiling the wort. Both are effective in removing suspended proteins by bonding to them and causing the proteins to settle out of the brew.
Dissolve 1 tsp of gelatin in warm water, and stir it into a fermenter containing up to five gallons of beer. It will take 4 to 5 days for gelatin to clear the beer before bottling.
Stir 1/2 tsp of Chilguard into 1/2 cup of hot water, and gently stir it into the beer in the fermenter. Chilguard is finely powdered silica gel, the same substance used in packaging to absorb moisture from the air. It effectively removes suspended proteins from the beer.
Remove polyphenols from the beer by stirring in Polyclar, a powdered plastic. It has a strong positive charge, and will remove the polyphenol molecules from the beer.
Unflavored gelatin can be found at any supermarket. The remaining fining agents can be ordered or purchased at most home brewing retailers. Except for gelatin, all of the listed fining agents are vegetarian/vegan friendly.