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Colour Technology 2 Why are we using colours? 3 IdentificationIdentification BrandingBranding Convey a Mood or a Style ChoiceConvey a Mood or a Style.

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Presentation on theme: "Colour Technology 2 Why are we using colours? 3 IdentificationIdentification BrandingBranding Convey a Mood or a Style ChoiceConvey a Mood or a Style."— Presentation transcript:

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3 Colour Technology 2

4 Why are we using colours? 3 IdentificationIdentification BrandingBranding Convey a Mood or a Style ChoiceConvey a Mood or a Style Choice

5 Introduction to Colour Technology Assessment and Measurement of Colour Factors Affecting Colour Matching Methods of Colouring 4

6 Colour Assessment 1)Eyesight 2)Light Source 3)Size 4)Background Colour 5)Surface Finish 6)Metamerism 5 observer object light source

7 1)Human Visual System 6

8 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

9 The Rods and Cones 8

10 ConesRods 5 million per eye (more L 100 million per eye and M cones than S cones) Responsible for daylightResponsible for low-level (photopic) vision(scotopic) vision luminance ←scotopic→ ←mesopic → ←photopic → → → → → → → 9 Rod function Cone function

11 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

12 2)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

13 3)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.Hence, it is important when decorating to paint a sufficiently large area. 12

14 4)Background colour Colours viewed against a strong, vivid coloured backgrounds, appears very different against a neutral or pastel coloured background 13

15 5)Surface finish A high gloss finish always appears darker than a matt finish of the same colour 14 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 6)Metamerism

16 Colour Measurement 1)Colour Space 2)Metamerism 3)Colour Measuring Devices  Colorimeters  Spectrophotometers 4)Light Sources and Illuminates 15

17 Colour 16

18 1) 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 17

19 Colour Space 18 +a* +b* -a* -b* L*=100 L*=0 L* -a* +a* -b* +b* + L = Lightness - L* = Darkness + a* = Redness- a* = Greeness + b* = Yellowness - b* = Blueness

20 Colour Space - Delta E is the difference between two points in colour space, often use to determine a colour tolerance or specification 19

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 20

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 21

23 3)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! 22

24 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 23

25 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. 24

26 4)Light sources and illuminants The three most widely used are: D65Simulation of Daylight (Artificial Daylight) ANormal domestic tungsten light TL84 Standard fluorescent tube used in most shops and showrooms 25

27 Colour Matching 1)Standard Colour Systems 2)The Material 3)Colorants 4)Legal Restrictions 26

28 1)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 27

29 2)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 28

30 3)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 29

31 3)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 30

32 4)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 31

33 Methods of colouring 1)Dry Colour 2)Masterbatch 3)Liquid Colour 4)Fully Compounded Colour 32

34 1)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. 33

35 2)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. 34

36 3)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. 35

37 4)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 END of presentation 36

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