Glassine sheets are often used for interleaving, inserting specific-sized sheets between delicate artwork, documents, books, or photos to protect from damage. Once the glassine paper completes its journey through the supercalendering machine, it is rolled or sheeted. Free from waxes or coatings, glassine is a sustainable alternative to laminated counterparts. Plastic fragments and silicone coatings are typically less biodegradable. Many papers contain wax coatings or plastic laminates to achieve these protective benefits. As a result, supercalendaring makes glassine resistant to grease, air, and moisture – ideal barrier protection from many substances. ![]() This gives the paper a highly closed surface with improved density and very low porosity. The force generated by each progressive nip polishes both surfaces of the paper.Īt a cellular level, the supercalendering process breaks down the capillaries of the paper fibers. As the high-speed calenders spin, the soft rolls struggle to return to their original dimensions and buff the paper passing through the nips. Supercalendering machines are specifically designed to apply pressure, heat, and friction at high speeds through vertical, alternating stacks of hard polished steel rollers paired with softer fiber-covered cylinders (called nips). This process is completed by putting the paper through the calendaring process multiple times or, more often, by performing the pressing on a special machine with heated or cooled pressurized calendars. Glassine gets its uniquely smooth, transparent, and glossy properties through a process called supercalendering. “Calendering.” Reference Document for the Production of Pulp, Paper and Board, Matrix of Industrial Process Indicators, 8 Aug. This smooths the surface of the paper by pressing it between hard pressure cylinders or rollers - called calendars. The supercalendering process.Ĭalendering is the final step in the papermaking process. And finally through the dryer section of the papermaking machine. More of the water is squeezed from the damp mat as it passes through a series of roller presses. The fibers mat and intertwine as paper sheets begin to take form. There, the watery pulp slurry flows onto a moving wire cloth where most of the water drains through. The wood fibers that remain are now ready to be bleached and treated further with dyes, pigments, or additives to fit the desired grade and color before moving on to the paper machine. ![]() These properties are what make glassine so unique. By removing the lignin, the pulp produces a paper with a neutral pH level and higher resistance to changes in chemical, structural, or optical properties. If lignin remains in the pulp during bleaching, the chemical reaction with the bleach turns the lignin into hydrochloric acid, which can make the paper brittle and discolored over time. Removing all of the lignin from the fiber during the pulping process is a crucial step in making glassine paper. This process separates the pure cellulose fibers from the lignin and other substances. The pulping process cooks the wood chips under pressure in a variety of ion solutions to break the chemical bond of the lignin (the organic polymers that form the cell walls and support tissue in plants). The first step in the papermaking process is converting the trees into pulp (the fibrous raw material used to make paper). When logs arrive at the paper mill, they are completely debarked and sent to chippers, where they are cut into pieces for mechanical or chemical pulping. Once the trees are grown to a specific size, the virgin timber is felled, stripped of its branches and twigs, and cut for transport. Glassine is made from hardwood trees, primarily varieties of aspen, oak, birch, and gum.
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