Isinglass is a wine fining made from the byproducts of the fishing industry, specifically it is a gelatin made from the swim bladders of sturgeon and other fish. It has a dubious smell in dried form and is difficult to mix. If you allow it to get warm after mixing or you keep it too long after hydration it smells pretty foul. However, if used correctly, it is a very effective fining agent that can render a wine or other liquor crystal clear, and because it settles out completely none of its undesirable properties remain in the wine. Overall, if used properly, it is a very good fining. Even though it settles out of the beverage it is not vegetarian.
Until quite recently it was common for beers to have isinglass added when they were put into cask. Guinness contained isinglass until 2017, and many beers still do. When the cask is disturbed the isinglass helps the beer to settle to perfect clarity again pretty quickly, thus it continues to fine the beer even after it is shipped from the brewery. However it has obtained some bad press recently as consumers read that it is a fish byproduct, and vegans revolt against it. Some people label it “Fish guts in my beer” which is a tad dramatic given some of the other things humans eat! Nevertheless many breweries are discontinuing its use. In the craft beer industry there is also a trend to just wait longer for the beer to clear, or indeed, to serve it slightly cloudy with all its bitterness and other flavours unmodified by fining.
Isinglass will mellow the flavour of a beer by removing some of the flavour compounds, particularly hops. It will also reduce tannins in wine. For a white wine however the effect is largely desirable.
For best results the positively charged isinglass should be used in consort with the negatively charged Kieselsol, though added in sequence some days apart as described.
The finings I am using are “Magicol Isinglass Fining 250AS.” To use isinglass you need to follow a two step process. It takes at least a day to make the isinglass solution before you can add it to your liquor. Then clearing can take anything from a few days to a week or two, though it is often dramatically faster. During the fining process the liquor should be very cold, ideally below 5 degrees celsius for liquors that are served at fridge temperature. This helps to avoid a chill haze returning after fining when the liquor is refrigerated for serving. Most of the time though a cold room is sufficient.
First, make the isinglass solution. Take 100 ml of water at less than 14 degrees celsius and add some acid to adjust the pH to between 2 and 3. This can be achieved with 75% phosphoric acid using 0.5 ml added to the 100 ml water. Now measure and stir in 0.6 g isinglass. Stir well and place in the fridge. Return to stir a few times for a period of 24 hours. By then the isinglass should be dissolved, if not, continue stirring for longer. Once made this will last a few weeks in the fridge.
Unfortunately with isinglass often getting all the globules to dissolve and homogenise is rather difficult with stirring alone, and you may have to force it through a sieve.
While preparing the isinglass the day before pitching you can also add liquid Kieselsol at a rate of 0.25 to 0.5 ml per litre to your liquor and stir gently. This can be left for 24 hours while you labour to dissolve your isinglass. Do not worry if it causes no change in the liquor, it will act in consort with the isinglass the next day.
Once you have dissolved your isinglass you now have 100 ml of solution which should be added to your liquor at a rate between 4 to 13 ml per litre of liquor depending on how cloudy it is. If your liquor is nearly clear, opt for the low end of the addition rate, if it is distinctly cloudy, opt for the high end.
Put your liquor in a cold place, preferably on a stable elevated surface where it can be racked off without moving the container then add the isinglass and stir gently. Leave for one to two weeks or until thoroughly clear and sparkling. Be careful that the sediment may be easily disturbed. If this is the case it may mean too much isinglass was used, but you can still rack your liquor carefully.