Burnishing gum is a substance with similar to properties to beeswax. It is used to coat the edges of leather work to protect the underlying leather and seal the edge from outside elements and wear. Burnishing gum also leaves a smooth, shiny surface on the leather edge that is quite visually appealing.
They’re generally available in synthetic and some more natural varieties. While beeswax is more commonly used, burnishing gums offer alternative options with sometimes different properties.