Gouache tubes and a "Chinese white" tube was added to boxes for this purpose. Later that century, for decorative uses "poster paint" was mass-produced, based on the much cheaper dextrin binder. It was sold in cans or as a powder to be mixed with water. The dextrin replaced older paint types based on hide glue or size. During the twentieth century, gouache began to be specially manufactured in tubes for more refined artistic purposes. Initially, gum arabic was used as a binder but soon cheaper brands were based on dextrin, as is most paint for children. A relatively new variation in
Gum arabic since antiquity, sub-Saharan acacia gum has a long history as a prized export. The gum exported came from the band of acacia trees that once covered much of the Sahel region: the southern littoral of the Sahara Desert that runs from the Atlantic to the Red Sea. Today, the main populations of gum-producing "Acacia" species are harvested in Mauritania, Senegal, Mali, Burkina Faso, Niger, Nigeria, Chad, Cameroon, Sudan, Eritrea, Somalia, Ethiopia, Kenya, and Tanzania. "Acacia senegal" is tapped for gum by cutting holes in the bark, from which a product called "kordofan" or Senegal gum is exuded. "Seyal" gum, from