This method works more subtle than the previous ones. Especially heated beds form a seemingly indestructible bond with the printed material sometimes.
So the first step after a print has finished is to let the printer and the heated bed cool down completely. If you’re lucky, the print pops right off afterwards. Otherwise, you can utilize the fact that the material properties of the plastic and the print platform – glass, aluminium or also plastic – are different. When the material gets colder, it contracts, and the different amounts of contraction cause the bond to break.
You can take advantage of this behaviour and use more extreme temperatures. Dropping a cool pack on the 3D print (try to cool down only one element- platform OR object) will increase the difference. It also works with canned CO2 or the “air duster” cans you can get at the hardware store. If you hold them upside down, the liquid leaks out. When it changes its aggregate state from liquid and evaporates, it absorbs energy, cooling down the area rapidly. Putting the build plate with the object in the fridge or freezer for half an hour works in many cases, too.