Propolis season. Normally, it is dark brown in color, but it can be found in green, red, black, and white hues, depending on the sources of resin found in the particular hive area. Honey bees are opportunists, gathering what they need from available sources, and detailed analyses show that the chemical composition of propolis varies considerably from region to region, along with the vegetation. In northern temperate climates, for example, bees collect resins from trees, such as poplars and conifers (the biological role of resin in trees is to seal wounds and defend against bacteria, fungi and insects). "Typical" northern temperate
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