Blends are usually taken to mean blends of different grape varieties, of which classic examples include Bordeaux (Merlot, Cabernets Sauvignon and Franc), Champagne (Chardonnay, Pinots Noir and Meunier) and the southern Rhône’s ‘GSM’ (Grenache, Shiraz and Mourvèdre). The science behind the technique is that it usefully combines wines with different but complementary traits (e.g. high acid and low-acid, or pale colour and deep colour) to make a more balanced, complete wine.
‘Pure’ unblended wines are rare as even varietal wines (i.e. those made from just one variety) will usually be blends of juice from different vineyards or vats, as producers seek to create and maintain a certain wine style. It’s worth remembering too that wine regulations in many jurisdictions allow for up to 15% of wine from a grape, region or vintage that is different from what the label says — so a ‘2014 Sonoma Valley Pinot Noir’ might (totally legally) contain 15% Syrah picked in 2012 in neighbouring Mendocino!
Image: Gregory Dubard of Château Laulerie practicing the art of blending; © Vignobles Dubard.