In his article on Chile, Alder (Vinography) wrote:
Carmenere is Not a Good Candidate for Natural Winemaking
I was surprised to learn that nearly 100% of all Carmenere wines made in Chile are acidulated. For those unfamiliar with the term and practice, this means that the winemaker adds tartaric acid to the wine during the winemaking process to boost the acid levels of the finished wine. Wines without enough acidity don't taste very good, of course. Carmenere, by the time it gets fully ripe, apparently doesn't have enough acid to make a well balanced wine on its own. At least not the way it is grown in Chile at the moment. So apparently Chilean winemakers are faced with only two choices: add acid, or blend in other grapes that can correct the lack of acidity. I was told by several winemakers that they used Petite Verdot for this particular trick, but if they wanted to make a 100% Carmenere wine, they would most certainly have to add acid.
"I went on a rigorous diet that eliminated alcohol, fat and sugar. In two weeks, I lost 14 days." Tim Maia, Brazilian singer-songwriter.