Shiny paper, also known as coated or gloss paper, is made of paper coated with a mixture of materials, often including polymers, to give it a glossy surface.
Components of Shiny Paper Coating
The coating applied to paper to make it shiny is typically a complex mixture designed to improve various properties, including appearance and printability. The exact composition can vary depending on the desired characteristics of the final product, but common components include:
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Binders: These are adhesives that hold the coating ingredients together and to the paper surface. Common binders include:
- Starch: A natural polymer derived from plants.
- Latex: A synthetic polymer, often acrylic or styrene-butadiene.
- Protein: Such as casein (derived from milk).
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Pigments: These provide opacity, brightness, and color to the coating. Common pigments include:
- Clay (Kaolin): A naturally occurring mineral that provides smoothness and opacity.
- Calcium Carbonate: A white mineral that improves brightness and opacity.
- Titanium Dioxide: A highly reflective pigment that provides exceptional whiteness and opacity.
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Additives: These are used in smaller quantities to modify specific properties of the coating. Examples include:
- Dispersants: To keep the pigments evenly distributed in the coating.
- Lubricants: To improve the coating's smoothness and prevent cracking.
- Optical Brighteners: To enhance the paper's whiteness.
The Coating Process
The coating is applied to the paper in a thin layer using various methods, such as blade coating, air knife coating, or cast coating. After application, the coating is dried and often calendered (passed through rollers) to further enhance its smoothness and gloss.
Resulting Properties
The coating gives shiny paper several desirable properties:
- High Gloss: The smooth, even surface reflects light, resulting in a glossy appearance.
- Smooth Surface: Improves printability and allows for sharper images.
- Reduced Ink Absorbency: The coating prevents ink from soaking into the paper, resulting in brighter colors and less ink usage.
- Improved Opacity: The coating makes the paper less transparent, which is important for printing on both sides of the sheet.
In conclusion, shiny paper achieves its glossy appearance and enhanced printability through a coated surface composed of binders, pigments, and additives, carefully applied and processed.
