Now that you have tested the wine for cold stability, turning it down to at least 30 degrees for about 3 weeks, and heat or protein stability, treating with bentonite as needed, it is time to see if you have corrected your stability problems. In order to do this, you must test the wines in exactly the same manner as you did originally (as described in my previous posts, The wine must be stable, even if the winemaker is not, and Protein Stability: Wine should not be a good source of protein).
After testing the wines again, you may find they need additional treatment. If you are still having protein problems, more bentonite must be mixed in. If there are tartrate crystals in your cold stability test samples, the wine needs to chill longer. Try testing it again in another week.
Once everything looks good, it’s time to talk about filtration (not to be confused with flirtation, which more commonly happens after the wine is consumed). Filtration is necessary to remove unwanted particles from the wine, such as dead yeast cells and tartrate crystals. Something to keep in mind, however, is that bentonite will easily clog up the filter pads so you should draw the wine starting from the top down. In the winery, we would hook up the hose to the upper racking valve to start the filtration and then move into the side door of the tank, taking the wine out slowly until we reach the bentonite that has settled out. (see previous post, “Rack Em’ Up). The very important thing to keep in mind for this filtration is that this cold wine must be filtered at the temperature you have used for cold stabilization. If you let it warm up, some of the tartrate crystals could dissolve back into the wine, only to haunt you in the future by falling out in your bottled wine.
While tartrate crystals are aesthetically unpleasant, they are perfectly natural and there is no harm in leaving them in the wine. In fact, in other parts of the world, particularly Europe, some winemakers shun filtration, and even refer to the tartrates as “wine diamonds”, leaving them in the wine. Europeans are unconcerned with these particles in the wine but, in the United States, we expect everything to be squeaky clean. If tartrates are discovered in wine bottles, customers complain and the sale of those wines goes downhill.
This will be the first filtration of the wine and the filters need to be coarse (filter pads come in various levels from coarse to fine). Many people believe that, if their wine is cloudy, they will just give it a nice tight filtration and make it beautiful. Well, it doesn’t work that way. If you start with filters that are too fine, the filters will clog up very quickly, sometimes immediately, and you will have to tear everything down and start all over again. This is probably not good for your sanity; it’s certainly not good for the wine, and it’s not so great for your wallet either as filter pads are not cheap.
There is quite a lot to cover regarding filtration and my next post(s) will go into detail regarding how it is done, how it works, and different options. I will discuss how the equipment works, the different levels of filtration, filter sizes, when filtration is commonly done, and options for amateurs.