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  • 1. Colour Technology
  • 2. Why use Colours? Identification Branding Convey a Mood or a Style Choice
  • 3. Introduction
    • Assessment and Measurement of Colour.
    • Factors Affecting Colour Matching.
    • Methods of Colouring.
  • 4. Colour Assessment
    • Eyesight
    • Light Source
    • Size
    • Background Colour
    • Surface Finish
    • Metamerism
    observer object light source
  • 5. Human Visual System
  • 6. The Retina
    • Retina uses special cells called “rods” and “cones” .
    • Rods “sees” in black, white & shades of grey and tell us the form or shape. (Super-sensitive allowing us to see when it's very dark.)
    • Cones “senses” colour but need more light. Three types and each is sensitive to one of three different colours - red, green, or blue. Together these can sense combinations of light waves. (To see millions of colours.)
    • Rods and cones together process the light to give you the total picture.
  • 7. The Rods and Cones
  • 8. The Rods and Cones 5 million per eye (more L and M cones than S cones) 100 million per eye Responsible for daylight (photopic) vision Responsible for low- level (scotopic) vision Cone function Rod function scotopic mesopic photopic luminance Cones Rods
  • 9. Eyesight
    • Individuals perceive colour differently. Is “ Sky Blue ” the same as “ Pale Blue ”?
    • How many People are Colour-Blind?
    • Experts are “turned in” to Colours.
  • 10. Light source
    • A red object in red light, appear red - as all the red light is reflected.
    • A red object in blue light, appear black - as no red light to reflect back.
    • The difference between say daylight and the Tungsten Lights used in homes, could be significant!!
  • 11. Size
    • A small area of colour may look very different to a large area of the SAME colour.
    Hence, it is important when decorating to paint a sufficiently large area.
  • 12. Background colour
    • Colours viewed against a strong, vivid coloured backgrounds, appears very different against a neutral or pastel coloured background.
  • 13.  
  • 14. Surface finish
    • A high gloss finish always appears darker than a matt finish of the same colour.
  • 15. Metamerism
    • Change in appearance of a colour under different light source.
    • Describe the relative changes in colour between two samples, i.e. Good match in day light, different in fluorescent shop lighting.
    • Occurs when different colourants are used in each sample.
  • 16. Colour Measurement
    • Colour Space
    • Colour Measuring Devices
      • Colorimeters
      • Spectrophotometers
    • Metamerism
    • Light Sources and Illuminates
  • 17. Colour
  • 18. Colour Space
    • To measure colour objectively, to communicate differences in quantifiable terms.
    • Principle is that all colours can be inside a “Colour Space” i.e. this space being a sphere.
    • Each colour can then be give a position in the colour space.
    • Differences between colours can be quantified by comparing the values of the co-ordinates.
  • 19. Colour Space + L = Lightness - L* = Darkness + a* = Redness - a* = Greeness + b* = Yellowness - b* = Blueness +a* +b* -a* -b* L*=100 L*=0 L* L* -a* +a* -b* +b*
  • 20. Colour Space - Delta E a* b*  C*  H* is the difference between two points in colour space, often use to determine a colour tolerance or specification. S C S H
  • 21. Colour Space
    • A different system (Yxy) is used for transparent colours.
    • Y = percentage of light transmitted
    • x = balance between blue and red light
    • y = balance between blue and green light
  • 22. More on Metamerism
    • Two colours with the same L*,a*,b* values which are arrived at by a different route will show metamerism.
    • Their colour will be different if the light source is changed.
  • 23. Colour Measuring Devices
    • Colorimeters
    • Filters the reflected lights into Red, Green an blue lights and measure the relative amounts of each, then calculates the numerical lab value.
  • 24. Colour Measuring Devices
    • Spectrophotometers
    • Measure the reflected lights at regular intervals across the visible spectrum, then produces a graph of the spectrum of light reflected by the colour called the Spectral Curve.
  • 25. Colour Measuring Devices
    • Spectrophotometers more accurate than colorimeters.
    • Spectrophotometers better at identifying metamerism than colorimeters.
    • Differences between the human eye and colour measuring devices > Possible to have an accurate reading but does not visually look right!!!!
  • 26. Light sources and illuminants
    • The three most widely used are;
    • D65 Simulation of Daylight (Artificial Daylight).
    • A Normal domestic tungsten light.
    • TL84 Standard fluorescent tube used in most shops and showrooms.
  • 27. Colour Matching
    • Standard Colour Systems
    • The Material
    • Colorants
    • Legal Restrictions
  • 28. Standard Colour Systems
    • Colours presented as printed paper patterns books. (RAL and PANTONE system.)
    • Building industry has its own set of BS colours.
    • NCS (Scandinavian) a measuring system rather than a fixed set of colours.
  • 29. The Material
    • Processing temperatures and chemical characteristics, means a colourant can work in one polymer, but degrade or discolour in another.
    • The more different the standard material is to the match material, the less likely an accurate match.
    • A painted sheet match to Nylon 6.6, the colourants used in paint will not survive 290 o C.
  • 30. The colourants-Pigments
    • Very fine powdered chemicals dispersed in the polymers.
    • Poor dispersion results in a weaker colour and often a grainy surface.
    • Inorganic pigments are mineral based, i.e. Metal Oxides & Sulphides.
    • Organic pigments are chemical compounds, less heat stable and more difficult to disperse. Usually give richer and more vivid colours. Less pigment is required.
  • 31. The colourants-Dyes
    • Chemical substances that dissolves in the polymer.
    • Chemically interact, as such allows light to pass through. When use in transparent materials remain transparent.
    • A limit how much dye can be added to a polymer, the dye can bleed out!
    • Insoluble in Polyolefins.
  • 32. Legal Restrictions
    • Food, Medical and Toy - mainly base on purity and inability to extract the colourant from the finish item.
    • Cadmium pigments - base on the premise when the Plastic part is incinerated, they can release Cadmium metals. Applies mainly in the packaging industry.
    • If a colour is required for safety purposes, then Cadmium pigments can be use regardless of the Cadmium legislation.
    • Many companies have a “Cadmium Free” policy regardless of the details of the legislation.
  • 33. Methods of colouring
    • Dry Colour
    • Masterbatch
    • Liquid Colour
    • Fully Compounded Colour
  • 34. Dry Colour or Dry Blend
    • The colourants are mixed with the polymer. Some dispersion aids may be added and often a “wetting agent” to help bind the powder onto the surface.
    • Advantages : Cheap because the conversion cost is low. Quick to prepare. Very small lot.
    • Disadvantages : Can be very Messy, can affect drying, colour can vary with different machine due to dispersion.
  • 35. Masterbatch
    • Compounds contains very high levels of colourants (up to 80%), then mixed at a fixed ratio to give a specific colour.
    • “ Polymer Specific” - Carrier is the same material as the base material.
    • “ Universal” - Carrier will readily mix with a wide variety of polymers.
    • Advantages : Better colour control, cleaner and less drying problems than Dry-colour. A stock range of colours and specific colours can be develop.
    • Disadvantages : May not always be compatible with the base polymer. Accuracy depends on the Moulder with mixing.
  • 36. Liquid colour
    • Similar to masterbatches, contains a high level of colourants, but the carrier is a liquid.
    • Advantages : Better colour control than Dry blend. More even distribution than masterbatch. Stock range of colours.
    • Disadvantages : Special dosing equipment is required. Spillage is messy. Colour can depends on processing. Properties can be affected by the liquid carrier.
  • 37. Fully compounded colour
    • The colourants are added to the base Polymers, then extruded to encapsulate the colour into the polymer and is fully dispersed.
    • Advantages : Specific, accurate and controlled colours. The performance of the compounds is more predictable. Ease of handling.
    • Disadvantages : Less flexible than the other methods.
  • 38. A Polymer for Every Application