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Our paper making begins with pulp, either as slush (a blend of pulp and water) or as a semi-dry baled product, delivered to large storage tanks near the paper machines. At Catalyst, we blend varying combinations of mechanical pulps, kraft pulp, fillers, pigments and recycled newspaper and magazines to make our newsprint, directory and specialty papers. Depending on the desired characteristics and type of paper we are producing, we use a thermomechanical or kraft chemical process to make our pulp.
1. Wood chips
This is where paper making begins. A typical wood chip measures 40 x 25 x 10 mm. Each chip comprises primarily water, cellulose wood fibres and the binding agent lignin. To make paper, we need to first make pulp, which is the process of breaking the wood structure down into individual fibres.
2. Head box
Think of this as the mixing bowl. Depending on the paper product we are making, we mix together varying combinations of pulps and dilute them to form a thin, uniform slurry that projects from the head box out into the forming section. For newsprint, we mix a combination of thermomechanical pulp, semibleached kraft pulp and in some cases recycled newsprint. For kraft papers, we use chemical pulp and recycled newsprint.
3. Sheet formers
The next step is to remove water from the pulp mixture — which is 99 per cent water at this point. Using a combination of gravity, vacuum and centrifugal force, we reduce the water content to 85 per cent before going on to several stages of pressing and drying. On our newsprint machines, we use a twin-wire process to create an even pattern of fibres and filler particles on both sides of the sheet, thereby improving its printability.
4. Press and dry
We remove more water in these stages. We first squeeze the water out on a press, and the sheet then passes over and around dozens of steam-filled drums. By the time the sheet emerges, moisture content has been reduced to less than 10 per cent.
5. Calender stack
At this stage, we iron the now-dry paper between polished steel rolls or specially designed soft rolls, giving the paper a smooth finish and a precise and uniform thickness that reflects the customer’s stated specifications. What began as watery pulp in the head box is now finished paper. The entire process takes less than a minute.
6. Reels and rolls
In the final step we wind the paper tightly onto a large reel that’s as wide as a city street and weighs as much as 30 tonnes. We then cut the paper to customer-specified widths, wind it onto small rolls and envelop it in a vapour-barrier wrap for storage and shipping. Each roll can hold up to 20 kilometres of papers.
