Beeswax may arise from such cappings, or from old comb that is scrapped, or from the beekeeper removing unwanted burr comb and brace comb and suchlike.
Its color varies from nearly white to brownish, but most often is a shade of yellow, depending on purity, the region, and the type of flowers gathered by the bees.
Wax from the brood comb of the honey bee hive tends to be darker than wax from the honeycomb, because impurities accumulate more quickly in the brood comb. Due to the impurities, the wax must be rendered before further use.
The leftovers are called slumgum, and is derived from old breeding rubbish (pupa casings, cocoons, shed larva skíns, etc), bee droppings, propolis, and general rubbish.
The wax may be clarified further by heating in water. As with petroleum waxes, it may be softened by dilution with mineral oil or vegetable oil to make it more workable at room temperature.
Bees reworking old wax
When bees, needing food, uncap honey, they drop the removed cappings and let them fall to the bottom of the hive. It is known for bees to rework such an accumulation of fallen old cappings into strange formations.
When the beeswax from brood comb is rendered to produce clean wax, it leaves behind the pupa casings, skins shed by molting larvae, excrement from larvae, wax moth cocoons, and other residual debris included in the original material.
Less slumgum can be expected from rendering of cappings or honey comb. Slumgum is slightly heavier than wax and sticks to the bottom of the wax cake. It is brown to black in color, and burns readily. Melted slumgum can be poured over pine cones to make fire starters.
Lumps of slumgum are very attractive to bees, especially when heated by the sun. They can be used to attract bee swarms, and some people therefore prefer applying melted slumgum on the sides of supers.
Slumgum is also used as a fertilizer in some agricultural crops like ornamentals; it has been shown that slumgum contains several nutrients that are required for the growth of these crops.
Depending on how well the rendering was performed, slumgum may still contain significant amount of wax that is possible to extract in larger factories using more complex equipment.