How Paper is Made

Paper begins its journey as trees in forests around the world. Loggers carefully select and cut down trees that will become our paper products. These trees are transported to paper mills where they will be processed into the sheets we use every day. The most common trees used for papermaking include pine, spruce, and birch, though many other types can be used as well. Once at the mill, the trees are stripped of their bark and cut into small chips to prepare them for the next steps.

Keywords:

• Loggers
• Mills
• Bark
• Chips

Reasoning Question with Two Choices:

• When trees arrive at paper mills, would removing the bark be considered preparation or the final step in papermaking? (preparation)

Reasoning Question with a Predictable Answer:

• Before trees can be made into paper, they must first be cut into small _____. (Expected completions: pieces (65%), chips (25%), segments (10%))

Reasoning Question with a Range of Responses:

• Pine is a type of tree used for making paper. Can you name another type of tree?

Open-Ended Question:

• Why do you think certain types of trees might be better for making paper than others?

The wood chips undergo a process called pulping to break them down into fibers. There are two main methods for pulping: mechanical and chemical. Mechanical pulping uses grinders to physically tear the wood apart, while chemical pulping uses special solutions to dissolve the lignin that holds wood fibers together. Chemical pulping creates stronger paper but is more expensive and can harm the environment if not properly managed. The resulting mixture of wood fibers and water is called pulp, which looks like a soupy, oatmeal-like substance.

Keywords:

• Pulping
• Mechanical
• Chemical
• Lignin

Reasoning Question with Two Choices:

• If a paper company wants to produce stronger, more durable paper, would they likely choose mechanical pulping or chemical pulping? (chemical pulping)

Reasoning Question with a Predictable Answer:

• The mixture of wood fibers and water used to make paper is called _____. (Expected completions: pulp (80%), slurry (15%), stock (5%))

Reasoning Question with a Range of Responses:

• Chemical pulping is one method used in papermaking. What is another industrial process that uses chemicals?

Open-Ended Question:

• How might paper mills balance the need to produce paper efficiently with concerns about environmental impact?

After pulping, the next step is cleaning and bleaching the pulp. The pulp contains impurities like dirt, sand, and remaining bits of bark that must be removed. Special screens and filters catch these unwanted materials. Many paper products are then bleached to make them white, though this step is skipped for brown paper products like grocery bags. Modern paper mills often use oxygen, hydrogen peroxide, or ozone for bleaching instead of chlorine, which can create harmful byproducts. The cleaned and bleached pulp is now ready for the papermaking machine.

Keywords:

• Bleaching
• Impurities
• Screens
• Filters

Reasoning Question with Two Choices:

• If a paper mill wants to reduce environmental impact during the whitening process, would they likely choose chlorine bleaching or hydrogen peroxide bleaching? (hydrogen peroxide bleaching)

Reasoning Question with a Predictable Answer:

• Brown paper products like grocery bags skip the process of _____. (Expected completions: bleaching (75%), whitening (20%), processing (5%))

Reasoning Question with a Range of Responses:

• Screens are used to filter impurities in papermaking. What’s another industry or process that uses screens for filtering?

Open-Ended Question:

• How do you think paper products might be different if we didn’t have the technology to bleach them?

The papermaking machine is a marvel of engineering that transforms pulp into paper. First, the pulp is diluted with water until it’s more than 99% water and less than 1% fiber. This watery mixture flows onto a moving mesh screen called the wire, where water begins to drain away. The fibers start to bond together, forming a wet sheet. The sheet then passes through a series of rollers that squeeze out more water and press the fibers together more tightly. This part of the machine is called the press section.

Keywords:

• Diluted
• Wire
• Mesh
• Press

Reasoning Question with Two Choices:

• When pulp enters the papermaking machine, is it mostly composed of fiber or water? (water)

Reasoning Question with a Predictable Answer:

• On the papermaking machine, the wet fibers begin to bond together to form a _____. (Expected completions: sheet (70%), layer (20%), mat (10%))

Reasoning Question with a Range of Responses:

• The papermaking machine is an example of industrial equipment. What’s another type of machine used in manufacturing?

Open-Ended Question:

• How do you think the papermaking process might change in the future as technology advances?

After the press section, the paper sheet still contains about 60% water and needs to be dried. The sheet travels through the dryer section, which consists of large, steam-heated metal cylinders. As the paper wraps around these hot drums, the remaining water evaporates. The paper gradually becomes drier and stronger as it moves through dozens of these heated cylinders. Temperature and speed must be carefully controlled to prevent the paper from becoming brittle or developing wrinkles. Once dried, the paper contains only about 5-10% moisture.

Keywords:

• Evaporates
• Cylinders
• Drums
• Brittle

Reasoning Question with Two Choices:

• If the dryer section operates at too high a temperature, would the paper likely become more flexible or more brittle? (more brittle)

Reasoning Question with a Predictable Answer:

• In the dryer section of a paper machine, steam-heated cylinders cause water to _____. (Expected completions: evaporate (85%), disappear (10%), escape (5%))

Reasoning Question with a Range of Responses:

• Steam is used to heat the drying cylinders in papermaking. What’s another process or machine that uses steam?

Open-Ended Question:

• Why do you think it might be important for finished paper to still contain some moisture rather than being completely dry?

The nearly finished paper now moves to the calendering process, which gives it a smooth surface. Calendering involves passing the paper through a series of heavy rollers that polish the surface. The more times paper passes through these rollers, the smoother and shinier it becomes. Different types of paper require different amounts of calendering – printer paper needs to be smooth, while paper towels are left rougher. Some specialty papers receive additional coatings at this stage to make them glossy, water-resistant, or better for printing.

Keywords:

• Calendering
• Polish
• Smooth
• Coatings

Reasoning Question with Two Choices:

• Would paper towels likely receive more or less calendering than glossy magazine paper? (less calendering)

Reasoning Question with a Predictable Answer:

• The process of passing paper through heavy rollers to make it smooth is called _____. (Expected completions: calendering (70%), polishing (20%), finishing (10%))

Reasoning Question with a Range of Responses:

• Printer paper is a type of paper product that needs to be smooth. What’s another paper product that needs special properties?

Open-Ended Question:

• How might different paper coatings change the way we use paper products in our daily lives?

After calendering, the paper is wound into large rolls that can weigh several tons. These enormous rolls are called parent rolls and can be up to 30 feet wide. The parent rolls are then sent to converting facilities where they are cut into the sizes needed for different products. Some paper becomes standard 8.5 x 11 inch printer paper, while other rolls might become newspaper, paper towels, or cardboard boxes. Special cutting machines slice the large rolls precisely according to the specifications for each product. The cut paper is then packaged and shipped to stores and businesses.

Keywords:

• Parent rolls
• Converting
• Specifications
• Packaged

Reasoning Question with Two Choices:

• Would the process of cutting large paper rolls into smaller sizes be considered part of papermaking or paper distribution? (papermaking)

Reasoning Question with a Predictable Answer:

• The enormous rolls of paper produced at paper mills are called parent _____. (Expected completions: rolls (85%), reels (10%), spools (5%))

Reasoning Question with a Range of Responses:

• Printer paper is one product made from cut paper rolls. What’s another common paper product you might use?

Open-Ended Question:

• How do you think the paper industry decides what sizes and types of paper products to make?

Recycled paper follows a different path but ends up in the same place. Instead of starting with trees, recycled paper begins with used paper products collected from homes and businesses. This paper is sorted by type, with different grades going to different recycling streams. The sorted paper is mixed with water and chemicals to break it down into pulp again. The pulp must go through special cleaning processes to remove inks, adhesives, and other contaminants. Once cleaned, recycled pulp can be made into new paper products following the same steps as virgin pulp, though the fibers are shorter and may produce slightly lower quality paper.

Keywords:

• Recycled
• Contaminants
• Adhesives
• Virgin

Reasoning Question with Two Choices:

• Is paper made from recycled materials likely to have longer or shorter fibers than paper made directly from trees? (shorter fibers)

Reasoning Question with a Predictable Answer:

• When making recycled paper, special cleaning processes must remove inks, staples, and _____. (Expected completions: adhesives (65%), glue (25%), contaminants (10%))

Reasoning Question with a Range of Responses:

• Paper is one material that can be recycled. What’s another material that people commonly recycle?

Open-Ended Question:

• What might be some challenges and benefits of using more recycled paper instead of making all new paper from trees?

SOURCES:

• “Handbook of Paper and Board” by Herbert Holik (Wiley-VCH, 2013)
• American Forest & Paper Association, “How Paper is Made” https://www.afandpa.org/priorities/paper
• Paper Industry Technical Association, “Papermaking Process” https://www.pita.org.uk
• Environmental Paper Network, “The State of the Paper Industry” https://environmentalpaper.org/