Carboxymethyl Cellulose or Sodium Carboxymethyl Cellulose (its sodium salt) is a cellulose gum used in some bubble solutions. It is often called CMC. It usually is packaged as a white powder. In some countries (not the U.S., however), it is the primary or sole ingredient of wallpaper paste. So, recipes that call for wallpaper paste are usually making use of CMC. It has been reported that it is an ingredient in some commercial bubble solutions.