One of the many occupational hazards of working in the wine business is leftover wine. At the end of the day, most days, there is a half a glass or so in 3 or 4 bottles on my tasting bar. Being frugal as I am, I dare not waste it. For a long time, I would bundle up the multiple bottles and take them home to have over dinner. That's fine, but each day I had to haul all the empties out to the recycling container. I began to feel the cold stare of my neighbors and had the sneaking suspicion that they were secretly keeping count.

Then while having dinner with a winemaker pal of mine, he mentioned the fine art of wine blending and it got me thinking. I began to experiment with my leftover wine not only in an effort to relieve my overflowing recycle bin, but to understand the process. Before I left the store, I would blend the several wines into one bottle just to see what it tasted like.

Why do winemakers blend different varietals together? Why don't others?

First, you have to understand the rules. In California the producer does not have to tell you if they blend and what they use to blend as long as the named varietal (cabernet, merlot, chardonnay) is at least 75 percent of the content. The other significant 25 percent can be whatever varietal they want. If there is no one varietal at or above 75 percent, it is then called "table wine," or "meritage," or they give it a nickname such as Caymus' "Conundrum," Phelps "Insignia," Kathryn Kennedy's "Lateral" or the ever-famous "Opus One."

Second, there are different philosophical camps in the winemaking community regarding blending. In addition to the obvious "purists versus blenders," most recognize that some varietals generally need blending, while other varietals should be left alone.

The French region of Bordeaux leads the way through the ages in cabernet blending. California cabernet producers follow suit and generally when pressed, they'll admit throwing a bit of merlot, petite verdot, cabernet franc and other varietals into what their label claims is cabernet. Each of the additions adds a certain quality; cabernet franc adds aromatics and softens tannins, petite verdot brings a deep color, and so on.

I liken it to someone getting their hair dyed; yes, it's not my real color, but a little help doesn't hurt, it's still me underneath.

It's rare for a California cabernet to be 100 percent cabernet fruit, and even more rare for a cabernet to be from 100 percent vineyard-specific grown fruit. Nickel and Nickel, a producer in Napa Valley, is very proud of the fact that its cabernets are 100 percent cabernet from specific vineyards in Napa. At a recent tasting I was amazed at the complexity the wines exhibited—layers of berry, cherry, cocoa, mocha, rich tannins, and long, lingering finishes. It's tough to get all of these things using the chemistry of blending varietals; to get them all from one grape type from one vineyard is amazing. Of the five vineyard-specific cabernets I tasted, each had its own distinct character, yet each was created using the very same process (oak treatment, yeast, aging). What the taster recognized as the difference among them was 100 percent from the fruit.

While it is rare that cabernet is not blended, some varietals should be left alone. While it's accepted to blend cabernet, it is generally frowned on to blend pinot noir with any other varietal. This delicate grape should not be messed with. Pinot lovers can check for a clue; hold your glass of pinot noir tipped to its side and let the light shine through. If the wine is blended with any other varietal, it will lose its natural clear rim. Sometimes, in order to beef up the color of pinot noir, the winemaker will blend a bit of syrah with it. The result will deepen the color and change the flavor. Still, most pinot noir is a blend of pinot grapes from different vineyards and/or areas.

Sauvignon blanc often has a bit of semillon tossed in, and chardonnay is sometimes boosted by adding a dash of chenin blanc. But that's not all; you can even find the red grape syrah blended with the white grape viognier. And to add further confusion, many of the very old zinfandel vineyards in California were planted using multiple grape types in the same vineyard. Most common was zinfandel, petite sirah and alicante bouchet planted together. After decades, it sometimes becomes difficult to tell which grape is on which vine. This has come to be known as a "field blend."

There are wine-blending "kits" available on the market (check out www.bourassavineyards.com/kit.htm), and it's easy enough to experiment informally on your own. In the comfort of your own home, toss some merlot into your cab and taste it. Throw the last bit of zinfandel into a syrah and see what happens. Be brave. Be daring. The combinations are endless (but not always tasty).

The point is not to take away from the expert craftsmanship of winemakers; rather, it's to demystify the process in order to be more familiar with blends and what the winemaker may be thinking.

As our society becomes more comfortable with wine and the whole business of winemaking, wine will become more of a common beverage and less of a special event item. And maybe my neighbors won't count my bottles anymore.

Cara Finn is the owner of The Grapevine, a fine wine and cheese store and tasting bar. She can be reached at 408.293.7574 or at info@grapevine-wg.com.