Propolis while also collecting water and tree resin necessary for the production of propolis. The chemical composition and nature of propolis depend on environmental conditions and harvested resources. For centuries, beekeepers assumed that bees sealed the beehive with propolis to protect the colony from the elements, such as rain and cold winter drafts. However, 20th century research revealed that bees not only survive, but also thrive, with increased ventilation during the winter months throughout most temperate regions of the world. Propolis properties may include: The composition of propolis varies from hive to hive, from district to district, and from season to
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