Researchers typically perform winemaking experiments using small amounts of grapes. Few studies have actually evaluated both the repeatability and reproducibility of small-scale fermentations in Tempranillo and Cabernet Sauvignon. This study examines, for two different phenolic potential varieties, the repeatability and reproducibility of the small-scale red winemaking in 4 tank sizes (10, 25, 50 and 100 L), and how volume size may affect to the composition of the wine. Additionally, for each variety we carried out a commercial fermentation using a 2500 L tank. Medium size-tanks gave the best extraction for the phenolic composition. High repeatability was observed for alcohol content, pH and total acidity, anthocyanins and procyanidins for both varieties. This research gives a solid basis for validating the reproducibility of the small-scale fermentations of two different phenolic potential red grapevines andsheds new light on small-scale winemaking potentiality and limitations.