The French term or phrase: 'remontage' - (pumping over) is the drawing off of the grape juice or must from the bottom of a tank or open fermenters and pumping it over the cap (composed of grape skins that forms on the top) to extract colour, create even temperature distribution, more flavour and tannins when making red wine, plus ensure optimal extraction and that the cap doesn't dry out and develop unwanted bacterial spoilage.
Not all pump-over's are equal. There are many ways to pump over. Ask a number of winemakers how to handle a pump-over and be prepared to hear an array of answers.
With pump-over's, you have to decide on: how often, how many, how long, how warm, how many litres, how fast, how gentle...for each tank...and then adjust it to each stage of fermentation and to how the flavours and tannins progress. It is best if you also remember how you did it last year and how it tasted yesterday...and last year. Simply put, there are lots of reasons and ways to tinker with the pump over at each stage of fermentation.
Generally, pump-over's are more gentle and shorter when the grapes first go into the tank. At the start of fermentation it is effective, it is less so when done towards the end of fermentation. It is at this stage where the colour is slowly coming out of the skins and there isn't any heat or alcohol to help with extraction. Once the fermentation begins, the pump-over's become more frequent and longer in an attempt to pull out the best of the flavours by moving larger volumes of juice through the warm skins but the warmer it is, the faster the fermentation progresses and the less time it leaves to get all that the grapes have to offer. It can be common practice to pump-over a third to a half of the tank each time.
Whether it is once or five times a day, this is the time that we are hooking up to each tank, climbing on top, checking the cap, recording its Brix level, measuring temperature, tasting its progress and enjoying the most obvious sounds and smells of crafting red wine.