In a method of carbonating a beverage using a carbon dioxide diffusing stone, temperature is measured in a flow of that beverage immediately before the flow changes from laminar to effervescent, thereby obtaining a true temperature at which carbon dioxide is diffused into the beverage. In another aspect of the present invention, there is provided a portable controller having connectors joinable to a gas pressure regulator of a gas cylinder and to any one of several beverage carbonation containers. The portable controller has instruments therein for controlling a flow of carbon dioxide gas to the beverage in any one of the containers and for controlling a pressure gradient of the carbon dioxide gas in the beverage over a period of time. There is also provided an elongated carbon dioxide diffusing stone assembly having an elongated temperature probe well extending parallel to and immediately below a diffusing stone.
