In contrast, groundwood papers, originally made with mechanically ground pulp, are more like newsprint and retain the lignin which makes paper turn yellow and brittle. Groundwood is a contaminant in recycling systems for freesheet papers because it has shorter fibers and introduces lignin. Generally, recovered paper with groundwood is downgraded for lower end-use products like corrugating medium and tissue. The new groundwood papers used in copiers and printers cannot be recycled routinely into newsprint. Moisture is always present in paper but too much can interfere with copy paper performance.
Reasonable care can reduce problems.
Avoid storing paper in damp warehouses and keep paper in its sealed cartons and ream wrappers until it is used. Paper and copiers in air conditioned spaces have fewer problems. As these integrated mills produce recycled paper efficiently in huge quantities, costs will begin to drop. Many stand-alone deinked pulp mills serve paper mills without their own deinking capacity. When the federal Executive Order described below was published in 1993, many paper mills switched their recycled copy paper production to postconsumer content alone.