This document discusses color measurement and specular gloss measurement. It defines color as the wavelengths of light reflected or emitted from an object, and discusses key color terminology like hue, value, and chroma. Color measurement is important for quality control and specification. Specular gloss measures the shiny appearance of surfaces and films. Standard test methods for both color measurement using spectrophotometers and gloss measurement are provided, along with factors that can affect the measurements.

1.  Colour measurements
ARJUN K GOPI
1ST M.SC BPS
CBPST, KOCHI
 Specular Gloss

2. Colour measurements
 What is colour ?
Colour is a property of object that results from the particular wavelength
of light which they reflect or give out, producing a sensation in the eye.
The variable of appearance include glossiness or matness, opacity or
transparency, smoothness or toughness, metallic reflection or diffusion
surfaces. If these appearance characteristics are eliminated, what remains is
absorption of light by the object in such a way that some colours are
removed from the light and part is reflected or transmitted.

3. Terminologies
 Following terminologies are useful to understand colour theory.
 Value or lightness : Colour range from dark to light in which black being
the darkest, grey in the middle and white being the lightest.
 Hue : Color has basic difference appearance such as red differ form blue
green or yellow these distinction as called Hue.
 Chroma : Chroma is defined as the attribute of color perception that
express the degree of departure from gray of the same lightness.

4. Significance
 Colour measurement is required for quality control, developing product
specification and colour matching.
 Evaluation and measurement of colour in plastics are important for
several diverse and interrelated reasons.
 If colour is to be specified, it must be described in specific term and
should also be measurable.

5. Test method
 ASTM D 2244 – 09 : Standard practice for calculation of colour tolerances
and colour differences from instrumentally measured colour coordinates.
 ASTM D 1729 – 96 : Standard practice for visual appraisal of colours and
colour differences of diffusely – illuminated opaque materials.
 ASTM E 308 – 08 : Standard practice for computing the colours of objects
by using the CIE system.

6. Specimen and conditioning
 The test specimen is taken from representative material and is conditioned at
23± 2ºc and 50 ± 5% relative humidity for not less than 40hrs prior to test.
Equipment
1. Calorimeter
2. spectrophotometer

7. Calorimeter

8. Spectrophotometer

9. Procedure of spectrophotometer

10. Procedure of spectrophotometer
- The monochromatic light is obtained by allowing the beam of light to pass through a
prism or diffraction grating (monochrometer)
- The monochromatic light is directed through a cuvette containing the sample, and the
light that penetrates hits the photoelectric cell.
- The current developed by the photoelectric cell is translated into percent transmission or
absorbance through a galvanometer.
- Then you can read the absorbance on the galvanometer.
- Absorbance is also called extinction and optical density.

11. Factors affecting
 Angle of illumination : The optimal position of the light source and the
detector relative to the sample surface are 45ºand 0º or 0º and 45º
 Type of material : opaque materials do not transmit light. Light is either
directly reflected from the surface as white light or absorbed.
 Particle size : decreasing particle size increases the light scattering,
causing the sample to appear lighter in color.

12. Specular gloss
 Specular gloss is defined as the relative luminous reflectance factor of a
specimen at the specular direction. Gloss is a measure of light reflected
by the surface of plastic film.
Significance
 Specular gloss measure the shiny appearance of films and surfaces.
 It is used to compare two or more materials based on their appearance.
 Gloss is associated with other visual aspects of surface appearance such as
reflected images, haze and texture.

13. Test method
 ASTM D 23 – 08 : Standard test method for specular gloss.
 ASTM D 2457 – 08 : Standard test method for specular gloss of plastic films and
solid plastics.
Specimen and conditioning
Specimen surfaces must have good planarity and free warpage, waviness or
curvature.
The test specimen is conditioned at 23± 2ºc and 50 ± 5% relative humidity for not
less than 40hrs prior to test.

14. Equipment

15. Procedure
 The instrument is turned on and placed on a black glass primary standard.
 The control knob is adjusted so that the meter indicates the value
assigned to the primary standard.
 The sensor is placed on the specimen surface and gloss value is read
directly from the analog or digital display.
 The instrument is calibrated regular intervals to ensure that the instrument
reading is particularly constant
 The instrument fails to repeat readings of the standard within 2% of the
prior setting, the intervening result should be rejected.

16. Factors affecting
 Surface property : Specular gloss is primarily due to reflection at the
surface, therefore, anything that changes the surface physically or
chemically is likely to affect the gloss.
 Surface of the material : It should be perfectly smooth. Smoothnes
depends on the quality of the surface of mold or die used to make the
part.
 Incidence angle : As the incidence angle increases, gloss value for the
surface also increases.