Fining Agents – Isinglass

(Positively Charged Fining Agent)

Many might be surprised to know that a commonly used fining agent in wine comes from the bladder of some fishes, usually sturgeon, cod or cichlids. It often comes packaged in some white wine kits as "Iso-Kleer," and is added to the wine after fermentation has taken place.

Isinglass, a form of collagen, is a positively charged substance, and when added to wine, it attracts negatively charged particles in suspension in the wine, and then drops to the bottom, aiding in clarification. Although it has been written about elsewhere on home winemmaking websites as being available in "sheets," this is likely a confusion with something called Isinglass made from the mineral, Mica.
Isinglass that is used in winemaking is available in a liquid or granular form. There is some debate over which form works better at clarifying wine. In his book, Techniques In Home Winemaking, Daniel Pambianchi writes

"Isinglass is available in liquid format used at a rate of up to 1ml/L of wine, or in powder format, used at a rate of between 1-3 g/hL of wine. The powder format has proven to be more effective."

Techniques In Home Winemaking.

However, in Home Winemaking Step By Step, Jon Iverson writes:

"Isinglass is available in both liquid and granular forms. The liquid form seems to clarify faster… with 1 – 2 ounces usually being right for 5 U.S. gallons (19 liters) of essentially clear wine."

~ Home Winemaking Step By Step

Considered a fairly benign agent as it does not remove as much colour as other positively charged fining agents.

Because it is a an animal product, many vegetarians have concerns about wines that have been fined with Isinglass, although any amounts of Isinglass that remain in the wine are negligible (if there is any at all).after the wine has been racked off the sediment after the Isinglass has done its job.

The vast majority of wine kits that have this fining agent provide it in the liquid form. There does seem to be some concern about a shorter shelf life of the liquid form, so if you are purchasing kits that have gone past their expiry date, you may want to remember to not only pick up a fresh package of yeast, but think about a fresh package of Isinglass if that is what the kit provides.