Natural glues are prepared from inert mineral sources, or organic sources such as vegetable substance, starch, natural resins or from animals e.g. casein or animal glue. They are often referred to as bioadhesives. One example is a simple paste made by cooking flour in water. Animal glues are conventionally used in bookbinding, wood joining, and many other areas but now are largely replaced by synthetic glues. Casein are mostly used in glass bottle labelling. Starch based adhesives are used in ridged board making and paper bagproduction, paper pipe winding, wall paper glues. Another form of natural adhesive is blood albumen (made from protein constituent of blood), which is used in the plywood industry.