By Evan Dawson, Finger Lakes Correspondent

Rosenthal After the recent discussion regarding the effects of filtration on wine, I contacted wine importer Neal Rosenthal for his thoughts.

Over the past three decades Rosenthal has been a leading voice calling for unfiltered wines. In his book Reflections of a Wine Merchant, Rosenthal writes often about how he routinely asked winemakers to stop filtering wines. He also wrote a brief defense of Brettanomyces, but he did not connect Brett and filtration in his book. I appreciate his response, and I learned a bit about the evolution of filtration. I'd love to hear from winemakers and industry professionals regarding the filtration techniques that Mr. Rosenthal discusses.

His comments are:

First, let me say that I am neither vigneron nor winemaker. And, I have never had the desire to delve in microscopic depth into the chemistry of wine. So, if I am an expert on this question, a label that I would reject by the way, it is only as a result of my 30+ years of experience buying and selling and drinking wine.

I have a preference for unfiltered wines. That being said, whether a wine is filtered or not is not the factor that determines its quality.  The most important elements in producing wine of quality is to have vines planted in the best places and to do fastidious work in the vineyards. The rest, I contend, is the easy part, although I am sure that those who consider themselves “winemakers” might object to that conclusion.

When I grew up in the wine trade in the mid-to-late 1970s, filtering was de rigueur and was done in a very aggressive manner. In my opinion, many wines had their growth stunted and their character shorn by the filtration process, then done via the filter plaque with tight fibers that truly stripped away important parts of the wine in exchange for clarity of color and security. Because of this, I strenuously objected to the filtering of the wines I was buying. This was particularly true in the case of wines that were aging for a considerable period of time prior to bottling because, in those circumstances, most of the deposit that might have accumulated was easily eliminated with a careful racking of the wine prior to the bottling. This, to me, was the safer and more sane way to treat wine rather than pumping a wine through a filter which, to my way of thinking, produced nothing of value. I never viewed filtration, in other words, as something done to improve the quality of wine. 

There have been dramatic changes in the way wines are handled now. The “kisselguhr” method appears to be less aggressive and, therefore, less harmful than the old filter plaque. Also, those who use the filter plaque now frequently resist using the most compact membrane. On the other hand, the process of filtering, no matter which method is used, forces the wine to undergo a process that I would argue is unnecessary. Why manipulate a wine to gain nothing. So, yes, I remain a devoted fan of unfiltered wines. 

That being said, I have participated in tastings of wines that I have purchased from my growers alongside the same wine that my grower had filtered and have come away on occasion preferring the filtered version. I think this occurred not because the filtering improved the wine but as a result of the fact that the wine bottled for us was drawn from a single barrel and the other cuvée was a blend of multiple barrels. As anyone knows who has been around wine cellars frequently enough, each barrel has its own special characteristics and each plays a role in developing the personality of the wine within. 

The bottom line is that good vineyard work and the harvesting of healthy, ripe grapes are the essential elements in producing top-flight wines and my goal is to protect those wines from anything that might change or diminish them. Filtering seems to me to be, in most instances, unnecessary and, perhaps worse, deleterious.


Neal I. Rosenthal
Rosenthal Wine Merchant Ltd.