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
Wood glue normal wood bending can break the bond in some applications. Often, too much adhesive is applied which leads to a much weaker bond. CA has quickly become the dominant adhesive used by builders of balsa wood models, where its strength far exceeds the base materials. Casein glue was used to make strong and robust joints in early aviation, but fell out of favor due to its susceptibility to attack by bacteria. Polyvinyl acetate (PVA), also known as "white glue" or "hobby and craft", is non-toxic and very easy to use, but hard to repair since most glues (including PVA itself)