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 gel strength, a measure of how many grams of force it requires to depress a plunger into a 12.5% protein solution of the glue at . Glue is manufactured in standard grades from . strength is the most commonly used for woodworking; is the highest normally used for instrument building; is the lowest used for general woodwork. Glue above strength requires excessive dilution and so leaves too little glue in joints for effective adhesion, so it is not commonly used. Liquid versions of hide glue are now available; typically they have urea added to keep the glue liquid at room