propolis is a resinous mixture that honey bees collect from tree buds, sap flows, or other botanical sources. It is used as a sealant for unwanted open spaces in the hive . Propolis is used for small gaps (approximately 6.35 millimeters (0.3 in) or less), while larger spaces are usually filled with beeswax . Its color varies depending on its botanical source, the most common being dark brown . Propolis is sticky at and above room temperature. At lower temperatures it becomes hard and very brittle.