Recycled pulp is paper from which the ink has been removed and the paper fibers released. In this form, the material is ready to be used to make paper again. It is also known as deinked pulp (DIP).
When it is first cleaned and separated, recycled pulp often looks like a pile of dirt or snow, depending on the dominant color of the paper. It can then be pounded into sheets or refined further to create new products.
The paper used for making recycled pulp is delivered to paper mills wrapped in bales. Then the paper is separated by grade or type. A conveyor belt then moves stacks of paper through the pulper.
Water, chemicals, and chopping blades are used to break down paper in the pulper. The process first breaks the paper down into fibers. Then it melts into the mush which is recycled pulp.
For the most part, recycled pulp is made out of clean discarded paper. It does not contain significant amounts of food particles, metal, or plastic. As it is impossible to collect completely clean paper in large volumes, some matter is removed from it during the pulping process.
The process of extracting unwanted matter from recycled pulp is called screening. It consists of forcing pulp through screens in order to catch these particles. This process can eliminate things such as small pieces of glue or plastic. Once it has been screened, the pulp is often cleaned further. It is funneled into cone-shaped cylinders which weed out other refuse by catching it in the bottom of the containers or throwing them out as they turn around.
After cleaning pulp, the ink and any other flat residue such as label glue is removed in a process called deinking. The first step is to run water through the pulp. Then if ink still remains, it is put in a vat with chemicals called surfactants, which, combined with air, remove the rest of the coloring and deposits it into bubbles which are then skimmed from the top of the pulp.
There are several products that use or are completely made out of recycled pulp. Some of the most common include toilet paper and newsprint. Several kinds of writing and printer papers also contain a high percentage of the pulp.
Special machines process recycled pulp so that it can be made into new products. Some of these are constructed so that they conserve water, make little use of electricity, and otherwise continue the spirit of conservation in the process. Many of these machines are semi-automatic and require a fair amount of human interaction.