The document discusses mottling, or cloudiness, in metallic coatings. It describes different types of mottling caused by orientation, thickness variations, and interactions between basecoat and clearcoat layers. Methods for evaluating mottling include using multi-angle spectrophotometers, cloud reference panels, and visual checks. The optimal size for perceiving mottling visually is between 50-100mm. A new instrument is presented that uses optical scanning to measure mottling over sample areas of at least 300x500mm, classifying mottling into size ranges. Graphs show how mottling levels correlate with texture and vary between coating colors and angles of observation. Charts provide examples of classifying mott

1. cloud-runner
Measurement of Mottling
Sandra Weixel, BYK-Gardner GmbH
7th Eurocar Congress, Barcelona – November 2011

2. Mottling / Cloudiness of Metallic Coatings
irregular areas of lightness variation
● undesirable defect at effect coatings
● especially noticeable on large body panels
● most obvious on light metallic finishes
Page 2, BYK-Gardner GmbH, cloud-runner

3. Causes and Cloud types
Orientation clouds
Disorientation influenced by wetting behaviour,
rheology additive or application method
Clear Coat
Base Coat
Disorientation influenced by interaction between
clearcoat and basecoat: Strike-in effect
Clear Coat
Base Coat
Page 3, BYK-Gardner GmbH, cloud-runner

4. Causes and Cloud types
Thickness clouds
Thickness variations result in poor hiding
Clear Coat
Base Coat
Thickness variations result in partial hiding
at grazing angle
Clear Coat
Base Coat
Page 4, BYK-Gardner GmbH, cloud-runner

5. Mottling / Cloudiness of Metallic Coatings
How is it evaluated today ?
● There is a high interest in objectively measuring “mottling”.
● In R&D applications multi-angle spectrophotometers are used to
measure lightness variation by “scanning” surface point by point.
● Very time consuming (fingerprint system analysis)
● Some companies have developed cloud reference panels
as a ranking tool.
● Most companies perform a visual check
Page 5, BYK-Gardner GmbH, cloud-runner

6. Perception of Mottling
Depending on illumination, viewing angle, distance and size
Page 6, BYK-Gardner GmbH, cloud-runner

7. Evaluation of Mottling
Which pattern size is perceived as mottle?
● Experts and non-experts mainly recognize mottle sizes between
50 to 100 mm. Extremes ranged from 25 to 200mm.
● Therefore, for visual inspection and measurement a min. sample
area of about 300 x 500 mm is recommended.
100mm
200mm
50mm
25mm
Page 7, BYK-Gardner GmbH, cloud-runner

8. How to measure Mottling
Scanning the mottle pattern
scanning 10 …100 cm
Page 8, BYK-Gardner GmbH, cloud-runner

9. Measurement
Optical principle
Illumination Detection 15°
15° to perpendicular Specular Reflection
Detection 45°
Detection 60°
Spot size approx. 4x4 mm
Page 9, BYK-Gardner GmbH, cloud-runner

10. Measurement
Minimize the influence of tilting
Illumination Detection +15°
15° to perpendicular Specular Reflection
Detection -15°
Sample surface
Page 10, BYK-Gardner GmbH, cloud-runner

11. Measurement
Minimize the influence of tilting
Illumination Detection +15°
15° to perpendicular Specular Reflection
Detection -15°
Object Curvature
Sample surface radius > 500 mm
Page 11, BYK-Gardner GmbH, cloud-runner

12. Measurement
Cloud ranges
The signal is separated by mathematical filters:
Visibility
Mottle Size min. scanlength
Md 6 - 13 mm
Me 11 - 24 mm
Mf 19 - 42 mm 130 mm
Mg 33 - 72 mm 230 mm
Mh 57 - 126 mm 420 mm
Mi 100 - 200 mm 750 mm
Page 12, BYK-Gardner GmbH, cloud-runner

13. Evaluation of Mottling
Which pattern size is perceived as mottle?
Small Mottles Large Mottles
10
9
8
7
6
5
4
3
2
1
0
Md Me Mf Mg Mh
6-13mm 11-24mm 19-42mm 33-72mm 57-126mm
Page 13, BYK-Gardner GmbH, cloud-runner

14. Evaluation of Mottling
Texture & Mottling
Small Mottles Large Mottles
12
10.0 11 Sample 1
9.0 Probe_1
10 Sample 3
8.0 9
Sample 5
Large Mottles (LM) 15°
Probe_3
8
7.0
7
6.0
Probe_5
6
5.0
5
4.0
4
3.0
3
2.0
2
1.0 1
0.0 0
6-13mm
M15d 11-24mm
M15e 19-42mm
M15f 33-72mm
M15g 57-126mm
M15h 0 1 2 3 4 5 6 7 8 9 10 11 12
M15d M15e M15f M15g M15h
Small Mottles (SM) 15°
Small Mottles = (Md + 0.5Me) / 1.5
Page 14, BYK-Gardner GmbH, cloud-runner

15. Evaluation of Mottling
Texture & Mottling
Mottling is dominated by the max value of the large mottles
10.0
9.0
8.0
7.0 Large Mottle: avg. max.
6.0 Sample A 3.8 4.6
5.0
Sample B 3.7 3.8
4.0
3.0
2.0
1.0 LM = (0.5Mf + max (Mg,Mh)) /1.5
0.0
6-13mm 11-24mm 19-42mm 33-72mm 57-126mm
M15d M15e M15f M15g M15h
SM = (Md + 0.5Me) / 1.5
Page 15, BYK-Gardner GmbH, cloud-runner

16. Evaluation of Mottling
Texture & Mottling - 2 dimensional graph
12
kaum sichtbare
11 Wolkigkeit
10
Visual Ranking:
sichtbare
9
Wolkigkeit
Large Mottles (LM) 15°
8
clearly noticeable
7 deutlich
sichtbare
visible
Wolkigkeit
6
5 hardly to recognize
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Small Mottles (SM) 15°
Page 16, BYK-Gardner GmbH, cloud-runner

17. Evaluation of Mottling
Texture & Mottling - 2 dimensional graph
12
kaum sichtbare
11 Wolkigkeit
10
Visual Ranking:
sichtbare
9
Wolkigkeit
Large Mottles (LM) 15°
8
clearly noticeable
7 deutlich
sichtbare
visible
Wolkigkeit
6
5 hardly to recognize
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Small Mottles (SM) 15°
Page 17, BYK-Gardner GmbH, cloud-runner

18. Evaluation of Mottling
Texture & Mottling
12
kaum sichtbare
11 Wolkigkeit
10
Visual Ranking:
sichtbare
9
Wolkigkeit
M Mottles (LM) 15°
8
clearly noticeable
Large– Mottling 15°
7 deutlich
sichtbare
visible
Wolkigkeit
6
5 hardly to recognize
4
3
M = LM * ( 1 - 0.05 * T )
2
1 T = SM - 6
0
-6
0 -5
1 -4
2 -3
3 -2
4 -1
5 0
6 1
7 2
8 3
9 4
10 5
11 6
12 7
13
T - Texture 15°
Small Mottles (SM) 15°
Page 19, BYK-Gardner GmbH, cloud-runner

19. Evaluation of Mottling
Texture & Mottling
12
11
10
Visual Ranking:
9
8
clearly noticeable
M – Mottling 15°
7
visible
6
5 hardly to recognize
4
3
M = LM * ( 1 - 0.05 * T )
2
1 T = SM - 6
0
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7
T - Texture 15°
Page 20, BYK-Gardner GmbH, cloud-runner

20. Evaluation of Mottling
Colors with Different Texture
10
15° 15° 10
60° 60°
10 10
9
White Pearl 9
Silver 9
White Pearl
White Pearl 9 Silver
8 8 8 8
7 7 7 7
6 6 6 6
5 5 5 5
4 4 4 4
3 3 3 3
2 2 2 2
1 1 1 1
0 0 0
Md Me Mf Mg Mh Mi Md Me Mf Mg Mh Mi Md Me Mf Mg Mh Mi 0 Md Me 0f Mg Mh Mi
20
15° 10
60°
18
Black Pearl 9
Black Pearl
16 8
14 7
12 6 no mottling visible
10 5
8 4
under 60° angle
6 3
4 2
2 1
0 0
Md Me Mf Mg Mh Mi
Md Me Mf Mg M6 Mi
White Pearl Black Pearl Silver White Pearl Black Pearl Silver
10 10
9 9
8 8
7 7
6 6
Mottling 60°
Mottling 15°
5 5
4 4
3 3
2 2
1 1
0 0
-6 -4 -2 0 2 4 6 8 10 12 14 -6 -4 -2 0 2 4 6 8 10 12 14
Texture15° Texture 60°
Page 21, BYK-Gardner GmbH, cloud-runner

21. Mottle-Chart
Example: Medium Class Models
12
11 Karossen
10 Body panels
9 Wolken deutlich
sichtbar
8
Mw - Mottling 15°
M – Mottling 15°
7
6
5
4
3
2
1
0
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
T - Texture 15°
Mc - Mottling Coverage
Page 22, BYK-Gardner GmbH, cloud-runner

22. Mottle-Chart
Example: Medium Class Models
12
Karossen
11
10 Body panels
Anbauteile
9
Add-on parts
Wolken deutlich
8 sichtbar
Mw - Mottling 15°
M – Mottling 15°
7
6
5
4
3
2
1
0
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
T - Texture 15°
Mc - Mottling Coverage
Page 23, BYK-Gardner GmbH, cloud-runner

23. Mottle-Chart
Example: Light metallic - Model 1
12
Karosse
11
10 Body panels
Anbauteile
9
Add-on parts
Wolken deutlich
8 sichtbar
Mw - Mottling 15°
M – Mottling 15°
7
6
5
4
3
2
1
0
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Mc - Mottling Coverage
T - Texture 15°
Page 24, BYK-Gardner GmbH, cloud-runner

24. Mottle-Chart
Example: Light metallic - Model 2
12
Karosse
11
10 Body panels
Anbauteile
9
Add-on parts
Wolken deutlich
8 sichtbar
Mw - Mottling 15°
M – Mottling 15°
7
6
5
4
3
2
1
0
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Mc - Mottling Coverage
T - Texture 15°
Page 25, BYK-Gardner GmbH, cloud-runner

25. Evaluation of Mottling: White Tricoat
Process Variations
15° 10
Left Front Door
Plant 1 15° 10 Left Rear Door
9 9
Plant 2
8 8
7 Plant 3 7
6 Plant 4 6
5 5
Plant 5
4 4
3 Plant 6
3
2 2
1 1
0 0
Md Me Mf Mg Mh Mi Md Me Mf Mg Mh Mi
10
60° 10 Left Front Door
60° Left Rear Door
9 9
8 8
7 7
6 6
5 5
4 4
3 3
2 2
1 1
0 0
Md Me Mf Mg Mh Mi Md Me Mf Mg Mh Mi
Page 26, BYK-Gardner GmbH, cloud-runner

26. Irregular mottle distribution
Measurement Hints
● Recommended sample area ~ 30 x 50 cm
● 10 scans in 1 - 2 cm distance
● min. scanlength: 42 cm for Mh
23 cm for Mg & M
Page 27, BYK-Gardner GmbH, cloud-runner

27. Example:
Striping and Measurement Direction
Paint application
Scan direction
Page 28, BYK-Gardner GmbH, cloud-runner

28. Example
Striping and Measurement Direction
Silver M 15° Left Hood Right Hood Door
10 10
15°
9 9
8 8
7 7
6 6
5 5
4 4
3 3
2 2
1 1
0 0
M15d M15e M15f M15g M15h M15i -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
6-13mm 11-24mm 19-42mm 33-72mm 57-126mm 100-200mm
T - Texture 15°
Page 29, BYK-Gardner GmbH, cloud-runner

29. Data Analysis with smart-chart software
Process Stability: Group by Color
Page 30, BYK-Gardner GmbH, cloud-runner

30. Data Analysis with smart-chart software
Process Stability: Selected Color shows Individuals
Page 31, BYK-Gardner GmbH, cloud-runner

31. Data Analysis with smart-chart software
Process Stability: Details shows Harmony
● Limit Curve: defined by the Tolerance settings
● Target Curve: indicates potential direction for improvement
Page 32, BYK-Gardner GmbH, cloud-runner

32. New: cloud-runner
Ideal tool for the production line
● Docking station:
- Recharging of battery packs
- Data transfer to PC
● USB port for data transfer to PC
● Software smart-chart:
- Organizer files for sample ID
- Data management with DB
- Standard QC Reports
Page 35, BYK-Gardner GmbH, cloud-runner

33. Thank you for your attention
Visit us in Hall 6 – Stand G-713