Wine tanks which have no permanent covers are called open-top tankes. They are typically used only for red wine fermentation. This is the traditional design for fermenters, but modern wineries now use only the closed-top design. Open top tanks are more difficult to keep clean, allow loss of volatile wine flavor during warm fermentations and require some type of surrounding building or roof in case of rain. (Wine,Beer,Spirits,Sake,Mead/Production)