A Sebastopol company that many winemakers consider their secret weapon against problem vintages has sold its California operations to a Napa wine services firm.

Vinovation, which specializes in high-tech filtration to remove excess alcohol and other unwanted substances from wine, has sold its Sebastopol operations to WineSecrets Inc. Terms of the deal were not disclosed.

Vinovation was started in 1992 by winemaker Clark Smith to commercialize a patent he received on his reverse osmosis technology for the wine industry.

The process removes unwanted substances and excess alcohol from wine by forcing it through a semi-permeable membrane.

Once frowned upon by the industry, alcohol removal has become a common tool for winemakers seeking to reduce alcohol levels to avoid the "hot" sensation associated with some high-alcohol wines.

Wineries also seek to reduce alcohol levels to lower their tax bills. Wines with more than 14 percent alcohol are taxed at a higher rate than wines with less alcohol.

The process also removes a variety of substances that can taint wine, such as the yeast brettanomyces and volatile acidity, which can give wine a vinegary taste.

The company serves about 700 winery clients and processes about 2 million gallons of wine every year, said Brian Smith, who joined his brother in the company in 1998.

It's the second-largest company of its kind in the industry. The largest is Santa Rosa-based Cone Tech, which uses a different technology -- spinning cones and centrifugal force -- to achieve the desired alcohol adjustment.

Vinovation's technology is licensed to about 10 clients in the United States and to about a half-dozen overseas, he said.

In February, WineSecrets, which specializes in mobile wine filtration technologies, acquired the mobile reverse osmosis business of Vinovation. WineSecret's key technology is a filter that removes naturally occurring salts in wine, a process called cold stabilization.

"Almost anyone who is anyone has worked with Vinovation in some way or another," said Eric Dahlberg, president of WineSecrets, who used to work for Vinovation.

As winemakers in California have chased higher-rated wines with more flavor, they have pushed the envelope on how late to harvest grapes, Dahlberg said. This often leads to higher sugar content in the grapes, and thus higher alcohol content in the wines.

Sometimes this is fine, but other times it's less desirable, and removing just a small amount of the alcohol can allow the wine's flavors to shine through, he said.

"Mother Nature throws you curves all the time, and there are not many wineries that are in the position to say, 'This wine wasn't what we wanted this year, so let's just dump it and start all over again next year,' " Dahlberg said.

WineSecrets will become a licensee of Vinovation's technology, he said. The company began taking over operations at the 45,000-square-foot facility in Sebastopol this week.

Vinovation owners Clark and Brian Smith will continue to hold the patent on their reverse-osmosis technology, and will continue to conduct research and development projects in the wine and nutraceutical fields, Brian Smith said.

They will also continue to pursue litigation against companies they believe to have infringed on their patent, he said.

You can reach Staff Writer Kevin McCallum at 521-5207 or kevin.