This appeared in last month's Winemaker Magazine. Short answer, always blend post-fermentation from finished wine.
Pícaro Mezcla de Vinos Kit (Outlaw Wine Blending for Kits)
Wine kits are a brilliant place to set your hand to doing some outlaw blending. Kit manufacturers have a wide selection of different wine types and styles so that you'll be able to make your own Super Tuscan or Rhone Ranger delight from existing wines, or make new ones on spec and do a big blending party.
1. Do blending from finished wine. Pre-fermentation blending is extremely tricky and may mess up fermentation and clearing schedules.
2. Have a goal in mind before you start. Are you trying to make your lean, dry Chianti sleeker and fatter? Want to bring up the tannin and blackberry on your Tempranillo? Itching for a customized GSM (Grenache, Syrah, Mourvèdre)? Write it down.
3. Blend wines of similar type: Pinot Noir and Mourvèdre aren’t on speaking terms, but Cabernet and Sangiovese are.
4. Decide what your 'base' is. This is the backbone of your blend, and what you're going to hang all of the other wines from.
5. Choose your adjunct wines, the ones you think are going to improve the base. Keep it to two at most, otherwise your palate will get fatigued and your intent may get lost.
6. DO NOT BLEND BAD WINE. It’s a waste. Throw bad wine away or give it to relatives with bad taste.
7. Always bench trial your blends—a three ounce mistake is easy to shrug off. 24 gallons, not so much
8. Blend wines of the same age. Well aged wines blended with younger ones seem jangled—simultaneously tired and green
9. WRITE IT ALL DOWN. As ever, if it turns out great, you’ll be able to do it again. If it’s a disaster, you’ll know what not to do.
When you've decided what you want to achieve, set up your bench trials with clear, disposable plastic cups and a set of graduated cylinders and syringes. Set up and label 5 cups and add to each one in succession 99 ml, 95 ml, 90 ml, 80 ml, 50 ml of your base wine. Then add in order 1 ml, 5 ml, 10 ml, 20 ml, and 50 ml of your first adjunct wine, so that each cup totals 100 ml.
Stir gently and taste each one in succession. Make careful notes and be aware if the wine seems to be reaching a better-tasting state that it can go past that and lose the edge.
Choose a winner and make up a half-litre of your blend, arrange 5 new cups and go through the same blending sequence with your second adjunct wine 99:1, 95:5, etc. Re-taste, and choose a final champion. Math it up--If you started with an 80/20 primary blend and used it at a rate of 80/20 with your second adjunct, the math for the first two is 80 ml x 80%=64 ml, 20 ml x 80%=16 ml, and your 20 ml second adjunct.
After that, it's just a wee bit more math and you're home free! Take your winner's 100 ml blend amounts, multiply them by 7.5 and that's how much you need for a bottle.
In our example
Base wine 64 ml x 7.5 = 480 ml
1st adjunct 16 ml x 7.5 = 120 ml
2nd adjunct 20 ml x 7.5 = 150 ml
Multiply that by the number of bottles your want and blend. For a dozen bottles of this blend
480 ml x 12 = 5.76 litres
120 ml x 12 = 1.44 litres
150 ml x 12 = 1.8 litres
Blend these amounts together, fill and cork a dozen bottles, and just like that, you're an outlaw winemaker.