Smaller berries = better skin to fruit ratio = more tannin.(Warmer years cater to produce small berries.) Petit Verdot and Cabernet Sauvignon have a thick skin and can extract associated with tannins. Wine Tasting is fun so don't make it a complicated, scientific project. Down the road . use tile, granite, reclaimed wine barrel flooring or cork. With most tastings, the focus is on fun first, education second.