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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 calledrodsandcones .
  • 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 Land M cones than S cones) 100 million per eyeResponsible 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

  • Aredobject inredlight, appearred- as all thered light is reflected.
  • Aredobject inbluelight, appearblack- as noredlight 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.
  • Principleis 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 betweenblueandredlight
  • y = balance betweenblueandgreenlight

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 MeasuringDevices

  • 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 (ArtificialDaylight).
  • A Normal domestic tungsten light.
  • TL84Standard fluorescent tube used inmost 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 accuratematch.
  • 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