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 high perishability of linen cloth and the solubility of hide glue. Well-known and relatively well-preserved — though substantially damaged — the most notable examples include Quentin Matsys' "Virgin and Child with Saints Barbara and Catherine" (c. 1515-25) and Dirk Bouts' "Entombment" (c. 1440-55). In German the technique is known as "Tüchleinfarben", meaning “small cloth colours”, or "Tüchlein", derived from the German words "Tüch" and "Lein" ("fabric" and "flax"). A binding agent for pigment was made by boiling animal skin mixed with other organic tissue and applied to linen, itself prepared with a thin layer of glue. The linen was ground,