Pipes smoking is the practice of tasting (or, less commonly, inhaling) the smoke produced by burning a substance, most commonly tobacco, in a pipe. It is the oldest traditional form of smoking. Spoon pipes (glass pipes or glass bowl pipes) have become increasingly common with the rise of cannabis smoking. Spoon pipes are normally made of borosilicate glass to withstand repeated exposure to high temperatures. They consist of a bowl for packing material into, stem for inhaling, and a carbureter (carb) for controlling suction and airflow into the pipe. These pipes utilize a two step process. First, the user inhales while lighting the smoking material and holding down the carb, allowing smoke to fill the stem. Then, the user releases the carb while inhaling to allow air to enter the stem and smoke to be pulled into the user's mouth.