Whipping cream will turn to butter very quickly as many folks have unhappily discovered right before dinnertime and the guests are waiting for dessert to be served. Overbeating, warm room temp. warm beaters & bowl etc will all contribute. And you don't end up with whipped butter, you get the fat separated out in clumps from the whey or "buttermilk" ...

That's why the mantra for whipping cream is to chill the bowl and beaters, and make sure the cream itself is cold, cold, cold. That's another reason why some manufacturers add the dextrose, gums, sorbate etc to commercial whipping creams ... it's to keep the fat globules dispersed evenly throughout the cream so they're less likely to clump, and so less risk of turning to butter. But it still happens. (ironically, the additives that prevent the cream from separating also make it harder to whip. )

Having the cream somewhat warm (a small amount in a small jar would warm to room temp fairly quickly) then agitating .. either by beating or shaking in a jar .. will cause the fat to clump together and separate out from the liquid. The whey ("buttermilk") could be saved and used in cooking, sauces, soup etc.

Word of warning, since it has happened to me ... it turns to butter in the twinkling of an eye! You will be whipping the cream, and think to yourself, "Oh, it's not quite thick enough" ... and so beat a little longer .... And next thing you know, it's separated into clumps ... and if you keep beating you end up with a ball of butter wrapped around the beaters, and a bowl full of liquid that is spattering all over you and the kitchen. Beware!!!

Doreen