Traditionally, glue is made from boiling up the bones, skins and other parts of animals such as fish
or horses in order to extract the gelatin, which is then purified and concentrated to make a sticky
substance that will form a bond as it dries. There are now many different types of glues, made from
plant material or minerals such as petrol, as well as different kinds of synthetic glues. One of the
simplest glues is flour-and-water paste and traditional wallpaper paste is made with starch. Latex
adhesives were originally made from the latex extracted from rubber trees, but synthetic forms are
now also available. Another type of synthetic glue is epoxy resin, in which the user mixes an adhesive
substance with equal quantities of a hardener. The two substances react chemically together, causing
the adhesive to set rapidly. Glues are widely used in many industries, such as furniture-making and food-
packaging.