Fill in the Blanks Fermentation - red winesOnline version Fill the gaps by Rita Bandirali 1 weeks rimontaggio CO2 paddle bottom dry cap removed higher 'autofermenter' follatura bodied insulating extracted microbes barrel ageing Vinomatic rotary tank wood days 'extended During red wine fermentation , a mass of skin debris called the floats to the surface , carried there by bubbles of . lf allowed to remain suspended , this cap will overheat and out , thus minimising extraction of colour ( especially ) and flavour components . A dried cap also becomes a repository for undesirable such as acetic acid bacteria . lf the skin cap remains intact for too long , it has an effect and creates temperature stratification in the fermenting . The temperature in the centre of the skins may be 10°C than the wine below it . Various methods exist for re - suspending cap material in the fermenting wine ; the simplest way is to physically 'punch' it back down into the liquid with a , something that can only be carried out in open fermenters . In Italian this method is called . Alternatively , wine can be pumped from the of the tank and discharged over the top of the cap ( called 'pumping - over' ) , thus irrigating and dispersing it . Various means of irrigation have been devised , the Ducellier system ( also known as the ) probably being the most useful . In Italian this method is called . Some wineries fit boards inside their tanks , which prevent the skins from floating to the top . Finally , there are now fermenters , which contain a system of internal vanes and revolve slowly about their long axis , thus ensuring thorough contact between skins and wine . Notable examples are the Rototank and the fermenter . The free - run wine will be from the fermentation vat when the required amounts of colour , flavour and tannin have been . The timing can vary from 2 to 3 post - fermentation , according to wine style . Some wineries leave the wine in prolonged contact with skins after fermentation has been completed , usually for a period of 2 or 3 weeks . This practice , which was a characteristic of Bordeaux wines , is called maceration' ; wines produced in this way have a better capability . With red wines , practicalities demand that they be almost completely fermented in tank ( to ensure appropriate extraction of colour and tannin from the skins ) before being transferred into a for the completion of fermentation . Any full - red wine can benefit from at least partial barrel fermentation , as the contribution of to the character of red wine is very important .