BS/EN 13523-22-2017 pdf download.Coil coated metals-Test methods Part 22 : Colour difference-Visual Comparison.
from strongly coloured neighbouring objects as well as direct sunlight should he excluded. The level of illumination shall he at least 2 000 lx and shall be uniform over the viewing area.
5.2 Artificial daylight
The evaluation area shall be shielded from external light, preferably by a permanent structure (lighting cabinet). The spectral characteristics of the light source should be equivalent to those of the CIE Standard Illuminant D65.
NOTE DIN 6173—2, 85950-1 and BS 950-2 provide procedures for measuring the actual spectral energy distribution over the viewed area.
The photometric conditions require an illumination between 1 000 lx (for very light colours) and 4 000 lx (for very dark colours).
The manufacturer of the artificial light source shall disclose the number of running hours which his product can be expected to conform to this European Standard.
5.3 Colour-matching booth
See also EN ISO 3668.
The colour-matching booth shall be an enclosure from which external light is excluded and which is illuminated by a light source giving a spectral power distribution falling on the test specimen, approximating to that of CIE Standard Illuminant D65.
The interior of the booth for general use shall be painted a matt neutral grey (the amount of a and b shall be less than 1,0) with a lightness L5 of about 45 to 55 (Munsell N4 to N5, NCS S 5500-N to S 6500- N), However, when mainly light colours and near-white colours are to be compared, the interior of the booth may be painted so as to have a lightness L’ of about 65 (Munsell N6. NCS S 4500-N) or higher in order to give a lower brightness contrast with the colour to be examined. When mainly dark colours are to be compared, the interior of the booth may be painted mart black with a lightness L’ of about 25 (Munsell mart black, NCS S 9000-N).
The CIELAR values stated are for the D65/10° condition and measured using 45°:0° as a reference. Alternatively, de:8° may be used for determination of colour values.
NOTE L, as and b refer to the CIE LAB system (EN ISO 11664-4).
To secure an appropriate surrounding field for colour comparison, the table surface in the booth shall be covered by a neutral grey panel. its luminance factor being chosen to be similar to that of the samples to be compared.
A diffusing screen shall normally be used to avoid the reflection of an image of the lamp from the test specimen. The spectral distribution properties of the lighting device shall include the spectral transmission of the screen.
7 Sampling
Shall be according to EN 135 23-0.
8 Test specimens and reference standards
8.1 Standards as well as test specimens shall be uniform in colour and gloss and free of imperfections and should preferably be flat. The preferred size of test specimens is about ISO mm x 100 mm. Specimens of a size at least larger than 120 mm x 50 mm should be used.
8.2 The standard coating shall have an acceptable light fastness, and its gloss and texture shall approximate those of the coating to be evaluated.
Since application, curing and film thickness contribute to the resulting colour, test specimens should be pre-treateci and coated (including application of a priming coat, if required) as specified. The dry film thickness should be determined in accordance with EN 13523-1.
9 Procedure
9.1 General
Evaluate the colour difference at ambient temperature. For more accurate comparisons, as required for instance in case of dispute, the ambient and panel temperature shall be (23 ± 2) °C and the relative humidity (50 ± 5) %, in accordance with EN 23270. Conditioning is carried out in accordance with EN 13523-0:2014, Clause 6.
9.2 Day-to-day routine
Evaluate each pair of test specimens under natural or artificial daylight. Place the specimens and the standard on a table or bench at the required distance from the light source to obtain the level of illumination required. The specimens and the standard should be placed in the same plane. View the specimens and the standard at a distance of approximately 500 mm. At this distance, the observer range should be 100 in accordance with ISO 11664-1. To improve the accuracy of the comparison, interchange the position of the specimens and the standard and again evaluate any deviations.
For metallics and differing levels of gloss, the acceptable procedure shall be agreed between the interested parties. When exceptionally coatings of widely differing gloss levels are to be compared, special viewing techniques are required.
The specimens may be compared either in natural daylight or in a colour-matching booth.
a) Viewing in natural daylight.BS/EN 13523-22-2017 pdf download.