Honey extraction abrading the surface of the wax with moving chains or bristles or hot knives. This, while messy, makes the process easier than doing this task manually. Some beekeepers will also harvest (before uncapping the honey) the propolis, a resinous material bees gather to glue the frames together; propolis is used for its medicinal properties. Once uncapped, the frames are then placed in a honey extractor, which spins them so that most of the honey is removed by centrifugal force. Care must be taken to ensure that all frames are loaded correctly, as the comb is angled slightly upwards to prevent
Glue-size but sometimes treated, by both the glue and also white chalk, which allowed a surface suitable for underdrawing and a base that would not absorb the final layer's pigment. The advantage of using glue as a binder is that the colours render as matte and opaque textures suited to austere or mournful images as opposed to the translucent appearance associated with oil. Many reds and blues bound in glue would have appeared with a brilliance and intensity difficult to achieve with oil. Unfortunately the surviving examples have greatly deteriorated over time, having suffered from colour alteration due to exposure to