1.5-The use of finishes Flashcards
Name some paper and board finishes
Laminating, embossing, debossing, varnishing (UV/spot), foil blocking. Printing processes (screen, flexographic/offset lithographic, digital).
Explain laminating finish
via encapsulation-sheet of paper encapsulated by polymer pouch
via surface coating-paper is coated with a liquid to seal and protect it
Explain liquid lamination
applied with a roller or spray and is used for applications like signage to protect from moisture, dirt and UV light (colour fading)
Explain film lamination
made of PP with and adhesive to make the laminate stick to the paper. Laminate is fed from a roller and pressure is applied as paper is fed through
Explain embossing
creates a raised design on the surface of the paper or card to give a visual and tactile effect. Uses a male and female die. Substrate sheet is placed between the dies and held under pressure
Explain debossing
produces an imprinted depression which sits below the surface of the paper/card.
Explain foil blocking
application of heat and pressure to a metallic paper to create areas of depth and texture to add aesthetic impact. Uses a machine with a heated die and the design is stamped onto the material through the foil, which is transferred as it is pressed into the paper. A foil sheet is placed between the die and the paper on which the foil is to be applied. Heat allows foil to stick to the paper. Requires accuracy and consistency in temp and pressure
What are the two types of paper varnishes?
Varnish is a clear ink used on pre-coated papers/boards for colour enhancement and protection. Gloss, matt, satin and tinted inks are used
UV varnish
Spot varnish
Explain UV varnishing
provides a smooth finish but ink must be completely dry before finish is applied. Varnish is applied with rollers and then passed under a UV light to cure
Explain spot varnishing
applied in specific areas
Explain screen printing
used for small print runs of items like posters or textile t-shirts. Substrate to be printed sits on the screen print machine base and the upper section secures the screen. Image to be printed is created on a screen, which is a mesh held by a frame. Screen has open areas for ink to flow through. Different screen required for each colour. Pigmented binding ink used is placed on the screen. A squeegee is used to force the ink to flow through the mesh onto the substrate
Explain flexographic printing
Preparation of Printing Plates: Flexible plates with raised images or text are created from a photopolymer material.
Ink Application: Quick-drying ink is applied to the raised areas of the plate.
Impression Cylinder: The plate is mounted on a cylinder, which rotates to transfer the inked image onto the substrate.
Drying: The substrate passes through a drying system to set the ink.
How many colours are used in flexographic printing?
4-cyan, magenta, yellow, black
Explain offset lithographic printing
Image Preparation: The image or text to be printed is transferred onto a metal plate, typically made of aluminum.
Ink and Water Application: The plate is treated so that the image areas attract ink and repel water, while the non-image areas attract water and repel ink.
Offset Cylinder: The inked image is transferred (or “offset”) from the plate to a rubber blanket cylinder.
Impression Cylinder: The rubber blanket cylinder then transfers the inked image onto the substrate (paper or other material).
Outline the key differences between flexographic and offset lithographic printing
Printing Plates: Flexographic uses flexible plates, while offset lithography uses metal plates.
Ink Transfer: In flexo, the ink is directly transferred to the substrate, whereas in offset, the ink is first transferred to a rubber blanket and then to the substrate.
Substrates: Flexographic printing can handle a wider range of materials, including non-porous surfaces, whereas offset is primarily used for paper.
Cost Efficiency: Flexo is generally more cost-effective for shorter runs and versatile media, while offset becomes cost-effective for large print volumes, especially on paper.
Print Quality: Offset lithographic printing typically delivers higher-quality prints with finer details and better color reproduction.
Explain digital printing
Image Preparation: The digital image or text is created and formatted on a computer.
Direct Printing: The digital file is sent directly to a digital printer, such as an inkjet or laser printer.
Ink/Toner Application: The printer applies ink or toner directly onto the substrate based on the digital file.
Drying/Fusing: The ink or toner is dried or fused onto the substrate using heat or UV light, depending on the printer type.
Explain key advantages of digital printing
Short Runs: Cost-effective for short print runs and on-demand printing.
Customization: Allows for easy personalization and variable data printing (e.g., unique names or addresses).
Speed: Quick turnaround times since no plates are required.
Quality: High-quality prints with fine details and vibrant colors.
Versatility: Capable of printing on a variety of materials, including paper, cardstock, fabric, and more.
How is colour added to polymers?
pigment added to the polymer during the manufacturing process or during the stock form manufacture.
Give examples of smart pigments used in polymers
thermochromic
phosphorescent
Explain acrylic spray paints
acrylic paint is a fast drying, water soluble paint that becomes water resistant when dry, and is used on many polymer applications.
What are some benefits of acrylic paints?
improved aesthetics
UV light protection
customisation
protection against weathering
Explain over mouldings
moulding a second polymer over specific parts of a product. TPE is often used, and over mouldings are primarily to provide areas of grip and texture, or to highlight different colours. There are two main ways of producing an over moulding:
-injection moulding moulds
-twin shot injection moulding
Name 9 metal finishes
cellulose and acrylic paints
electroplating
dip coating
powder coating
varnishing
sealants
preservatives
anodising
cathodic protection
Explain cellulose and acrylic paints
paints provide colour, a textured finish and a barrier against corrosion. The surface of the metal must be cleaned and degreased prior to paint application to ensure the primer coat has a good surface to grip
