Glycerin rivers are formed when cold process soap heats up during the saponification process and glycerin leaches and pools in the soap creating translucent lines of glycerin within the soap. These lines are visible as the soap is cut and are revealed as a seemingly "cracked" look. Fortunately, glycerin rivers do not affect the soap's function or quality--just the way it looks. Some soap makers find they actually enhance the look of the soap giving it a unique appearance, while other feel it interferes with the initial design.