ArticlePerfecting Pyment, Vinifera Vines, and Over-YeastingWritten by Alison Crowe. . . you could also buy some powdered grape tannin, use oak chips, or even use a cup of strong black tea to add some tannin backbone to the wine if it’d be tough for you to obtain grape skins.Already a member? Log InYou'll Also Like Article MEMBERS ONLY Cork Variability, MLF Question, pH Testing, and Aceto Problems A concerned reader asks the Wizard why commercially-purchased wines might have their corks raised. She also answers questions on metabisulfite use before malolactic fermentation, when to re-test for pH, and dealing with Acetobacter issues. Article MEMBERS ONLY Avoiding Sulfites, Adding Copper Pasteurization operates on a sliding scale and its effectiveness depends on a coefficient between time and temperature.