||This article needs additional citations for verification. (September 2011)|
A paper bag or paper sack is a preformed container made of paper, usually with an opening at one end. It can be one layer of paper or multiple layers of paper and other flexible materials. Paper bags are used for packaging and/or carrying items.
How Paper Bags are Made 
When people make paper bags, here are a couple things they can do to make them. Firstly, if they are using logs to make the paper, debarked logs are sent to dry in a mill for three or so years. Then, after they are dried, they are exposed to chemicals, heat, and pressure to make oatmeal like pulp. If the manufacturers are using recycled paper, the recycled paper is made into pulp first, because it doesn’t need to dry first. After the pulp is made, it is formed, cut, glued, packaged, and then sent to the receiver. If desired, a paper bag can be made at home from the same process with newspaper or any recycled paper Roof
There are also three credited inventors for the paper bag; their names were Margaret Knight, Francis Wolle, and Luther Childs Crowell. Margret Knight, also known as the mother of paper bags, invented the square bottomed paper bag; even though Crowell made a patent for it. Francis Wolle was the inventor of a machine to make the square bottomed paper bags. Wolle was a botanist, clergyman, and a teacher, who apparently had the money to make a machine on a teacher’s salary. Luther Childs Crowell was the man mentioned previous, who made the patent for the square bottomed paper bag. Luther acknowledged Knight as the true inventor, but declared that he had rights to make and sell the bag. He filed almost 300 patents.
Single layer 
Paper shopping bags, brown paper bags, grocery bags, paper bread bags and other light duty bags have a single layer of paper. A variety of constructions and designs are available. Many are printed with the names of stores and brands. Paper bags are not waterproof. Types of paper bag are: laminated, twisted, flat tap. The laminated bag, whilst not totally waterproof, has a laminate that protects the outside to some degree.
Multiwall paper sacks 
Multiwall (or multi-wall) paper sacks or shipping sacks are often used as shipping containers for bulk materials such as fertilizer, animal feed, sand, dry chemicals, flour and cement. Many have several layers of sack papers, printed external layer and inner plies. Some paper sacks have a polyethyelene foil or polyethylene coated paper layer in between as a water-repellant barrier.
There are two basic designs of bags: open mouth bags and valve bags. An open mouth bag is a tube of paper plies with the bottom end sealed. The bag is filled though the open mouth and then closed by stitching, adhesive, or tape. Valve sacks have both ends closed and are filled through a valve. A typical example of a valve bag is the cement sack.
Paper bags are readily recyclable. Plastic or water-resistant coatings or layers make recycling more difficult.
The first paper bag machine was patented by Francis Wolle in 1852. Margaret E. Knight (1838-1914) was an employee in a paper bag factory when she invented a new machine part to make square bottoms for paper bags. Knight can be considered the mother of the grocery bag; she founded the Eastern Paper Bag Company in 1870. On 20 February 1872, Luther Crowell also patented a machine that manufactured paper bags.
See also 
- Yam, K. L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009, ISBN 978-0-470-08704-6
|Wikimedia Commons has media related to: Paper bags|