Jason Joyce
January 26, 2012 | Chalk Talk | Jason Joyce

Filtering & Fining

     So there you are, all stressed out because of a big final exam tomorrow. You are confident you can pass the multiple choice part. If that was all the exam consisted of, you could be out having a drink and getting a peaceful night's sleep. Sadly, there are rumors of an oral exam. All alone on stage with various professors asking questions that you can't really prepare for. Well, if someone told you that students that skipped the oral exam not only passed, but were actually found to master the topic better than those that took the oral exam. Well, no brainer right, just skip it. I can't help but think of it in these terms when I'm told about unfiltered wines.
     Increasingly in recent years I've seen wine labels and tech sheets extolling the unfiltered & unfined nature of the wines. Unfined, sure, so far I've been able to avoid throwing eggs in my Cabernet or pouring bull's blood in your syrah. If you are confident that you picked your grapes at the right time, made and aged the wine soundly, not needing to fine makes perfect sense in small lot wine making. Filtering to me is an entirely different issue. I can't claim to tell you that one train of thought is better or worse. But after years of thinking, reading, asking and doing, I am fairly confident that neither is always better than the other.
     Give me a second here and let me tie back into that first paragraph. Bottling is the final exam for the winemaker. After 1-3 years of working with a wine, you mark a date that you are putting it in bottle. After that, you don't get to play with it ever again. It is marked as ready for the world, and you send it out to meet people. Thus those final couple of weeks are a flurry of nerves and activity. The blending trials are sure fun, and make one appear to be an actual winemaker. Dressed nicely while standing around contemplating glass after glass until you feel you've got the best final blend you can make.
     Next comes the forklift driving, hose dragging and barrel washing that require less fancy outfits and are more actual work. This is the part of the job you don't wax poetic about during a winemaker dinner. And then there is filtering, the job done 99.9% of the time by assistant winemakers or cellar crew. Let me tell you, nobody enjoys filtering. If you've worked with one, you would know. They take a long time to prepare, (pumping wine through wet cardboard and avoiding a TCA like wet cardboard flavor or aroma takes a bit of magic) then they inevitably clog up. You have to back flush and eventually prepare a new set of pads. The pressure builds up to scary amounts and you hear strange cracking and popping noises making you feel a hose or the pump could explode at any moment. And worst of all, you lose a certain percentage of your wine dripping off the pads. Man, if not using a filter makes the wine better, count me in. That's a couple days of my life back. Plus I could change back into my dry pants and Patagonia fleece vest and walk around the cellar like a proper winemaker. Leg up on a barrel, wine thief in hand, gazing thoughtfully into the distance....but I digress. Quite often, as troublesome as it is, I feel like filtering is often a necessary endeavor.
     To understand why, you first have to think about what is being filtered out of the wine. This is not a charcoal filter that is going to strip the wine bare. The filter is a cellulose sheet, kind of like a super heavy duty coffee filter. So you push the wine through the filter sheet, and the large impurities are taken out. These filters are not so fine that they remove the molecules that are associated with flavor or taste. What we're talking about are the dead yeast and bacteria, the byproducts of primary and secondary fermentation, that are suspended in the wine solution. This is what forms the thick mud like lees at the bottom of barrels of aging wine. Trust me, I've cleaned enough barrels and fermentation tanks to have a little lees end up in my mouth. These are not the flavors you're reading about in any wine critics tasting notes of fine wine. They also can make the wine appear cloudy, a massive fault in a bottle that tells me basically the winemaker doesn't care all that much.
     There are times I can avoid filtering. If I have been a busy beaver winemaker and racked the wine many times over. This means pumping the clear wine off the top and leaving the lees in barrel. If you do this a bunch of times, all those impurities will have naturally dropped out of solution, so the wine for the most part will be clear and free of most large impurities. If this is the case, well no need to filter. Gravity has done the work for you. But I don't rack my wines that often, usually just 1-2 times over wine's lifetime in the cellar. I feel lees is the wine version of the primordial soup, and all sorts of interesting things are taking place in there. Over the years in barrel, flavor, aroma, and mouthfeel components are being created in the lees and released into solution. Almost all barrel aged white wines are made like this. This along with malic acid and cold stabilization is why you almost never see unfiltered white wines. I strongly believe red wines can benefit from sur lie aging just as much as whites.
    The sacrifice I have to make for these lees components though is a couple of long, cold, wet days staring at a pressure gauge, getting that wine all cleaned up and ready for it's introduction to the word.


Jim Zweigle's Gravatar
Jim Zweigle
@ Mar 13, 2012 at 4:41 PM
This rainy afternoon we just opened your 2006 Tres Violets and are enjoying it as we speak. Remember spending part of an afternoon up in your patio, talking with a young chemist/winemaker (you?) and taking photos. Happy day. So we set the bottle upright and opened a half-hour later to discover a delightful sediment. No matter; read about sediment on the web and continued to drink contentedly with some blue cheese and leftover cold ribeye. Very complex character with a great finish. Kudos! Pls explain sediment.

Jason's Gravatar
@ Mar 15, 2012 at 10:46 AM
Jim, It was me you chatted up that day. Glad you enjoyed the Tres Violet. Sediment is rather common in any of our wines, especially Estate wines that have Cabernet and Mourvedre in them. The reason for this has to do with our soil. The sediment you find in the bottle is Potassium Bitartrate, commonly referred to as "Tartrate Crystals". They form naturally in aging wines as Tartaric Acid and Potassium react with each other. Due to our alkaline soils, we tend to have very low pH, high Tartaric Acid levels in our wines. Our Cabernet and Mourvedre vines are planted in a section of the vineyard that happens to have very elevated levels of Potassium that is taken up by the vines. This crystallization occurs most rapidly at cold temperatures. In fact, for white wines, we chill them to 32 degrees for 5 days before bottling in order to precipitate out all the crystals. For the most part, red wines are rarely kept in refrigerated conditions, so it is not a common practice to cold stabilize reds. But due to our elevated levels of the Tartrate building blocks, we tend to get crystals in our Tres Violet, Meritage, and Cab Sauv.

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