There are two distinctly different situations here. Kit Wine and Country Wines.
Because the juice used has been specially selected (and normally pasteurised) it is rare that we will experience a problem with clearing a kit wine. If the wine fails to clear it is nearly always down to two things. The wine hasn’t been sufficiently degassed or the wine was still slightly fermenting when the stabiliser (that’s potassium sorbate and sodium metabisulphate) was added.
I know people will say we have done this for years in the same way so how could this happen. Well, I can only give you the facts. Maybe the weather has gone colder at night which has slowed the fermentation. The liquid temperature of the water we added at the start was different. The yeast sachet in the kit was just a bit older than normal (still fine but can take a little longer to start the fermentation). The liquid wasn’t mixed properly at the start. We thought it had stopped fermenting as no bubbles were coming through the airlock (never take this as it's finished always do two readings on your hydrometer a day apart with then being the same). As you can see there are quite a few factors in the equation and there are more. So before you blame the kit the chances are it’s something you have done.
When we add the stabiliser sachet there are two parts to it. The Sodium Metabisulphate is the preserving agent that allows us to do things like bottling without getting an infection and Potassium Sorbate will stop the yeast from restarting. This is important because it will not kill a fermenting yeast when it's added. The yeast must have finished working for it to do its job. When added if there is a slight fermentation it will delay the yeast (sort of stun it so it looks like we have killed it) but then the yeast will wake up and start again.
The idea is that if it's fully finished the addition of the Sorbate will prevent it from working again (kill it) and this will mean we can add sugar to the wine to sweeten later without the worry of secondary fermentation.
So what’s the solution? What are the options?
It’s too late now but degassing is important for us to get rid of the carbon dioxide gas (this is given off when the yeast converts the sugars to alcohol) in the wine. If we don’t we will struggle to clear the wine. It’s also a good gauge of whether the wine has finished fermenting. If when we are degassing, we are continually getting heavy bubbles on the liquid surface the chances are we are it’s still fermenting.
Firstly, we can leave the wine a bit longer to see if it clears. The finings that come with a kit wine in the main are the two-part type (Kieselsol and Chitosan. These should always be left for 3-5 days. This is a bit naughty as for the finings to work properly it should be a minimum of 5 days (it’s put at 3 days to substantiate the ready in 7 days claim on the kit). Finings are quite vicious and they will strip out flavour, body, bouquet, and colour all things we want to avoid removing from wine. So the manufacturers will use as mild a form of finings as possible. If they are working mega quick, it’s not doing the wine any favours it might look good but that’s it.
So leaving it a little longer won’t hurt. The only thing we should be careful of is the fermenting container should have little headroom (space between the liquid and the lid of the container). It's fine for 5 days but much longer than this we run the risk of infection. So if this is the case we must put it into a perfect size container with little headroom. We love to use one-gallon glass jars (or PET plastic containers or our 23-litre glass or plastic carboy) if this happens so we don’t get headroom and we can also see if it's clearing.
If we are looking for a quicker solution and one more radical, we can simply add more finings. Some people will siphon the liquid of the worst of the sediment first but this isn’t necessary as the finings like the sediment the more present the easier it works (within reason). Again once added just let it do the work.
If the wine is still fermenting, we have a problem as there is no short term fix. We should move the container to a warm place and get the fermentation going again. Giving it a massive stir will also help get some air into the liquid. Once this has successfully finished we should go through the degassing, stabilising, and fining process again.
All the above will apply to Country Wines (fruit we pick from the bushes, soil, and trees) but we can end up with starch or a pectin haze depending on what type of wine we are making.
To avoid this, we should always add a pectolase (to prevent pectin) or an Amylase (to prevent starch) haze in the wine. Ideally this should be added at the start of fermentation (will help break down the natural flavours that come out of the fruit) but if it’s not it should be added at some stage in the making or clearing.