Colors

The desire to describe colors in a more precise way than we can verbally has been around for many years. In recent years, especially, as industrialization has grown - and with it the degree of specialization - ways and systems of defining colors independently of subjective perceptions have had to be found.
Wilhelm Ostwald, Professor of Physical Chemistry in Leipzig, developed a color system based on physiological perceptions and published it for the first time in 1917. The American painter Munsell also created a color system based on perception.
Both systems contradict the color teachings of the grand master, Goethe, who created his on the basis of color mixtures. His representation of the color circle is incorrect, since the relationships between the colors are not based on perception, but rather on physical mixing attempts.
In 1888, Ewald Hering published his "Lehre vom Lichtsinn ('A doctrine on the sense of color')", in which he set out the theory of opposing colors. According to this theory, red cannot be greenish and green cannot be reddish. Equally, blue cannot be yellowish and yellow cannot be blue-ish. These theories correspond to our perception of color, which is described physiologically but not physically. Ostwald and Munsell also graded their color systems numerically, allowing a precise description of each color. Their color systems also formed the basis of the first international color standard, which was published in 1931 by the CIE (Commission Internationale de l´Éclairage). With some modifications and improvements, the CIELAB system is still used all over the world today, and has more or less become established as a standard in practice.
The growing proportion of aluminum pigments used for manufacturing so-called "metallic" colors, especially in the automotive sector, gave rise to the need to create a precise and adequate method for describing and defining these colors and effect, as well. The previous methods of measuring bright colors with one geometry based on the angle of illumination and observation evolved to produce the multi-angle measurement.
This multi-angle measurement was based on the optical properties of aluminum pigments, which reflect light falling on them like a mirror. The intensity of the reflection diminishes as the glancing angle increases. Consequently, it was possible to measure using a fixed angle of illumination with varying differential angles to the glancing angle. 15°, 25°, 45°, 75° and 110° were defined more or less arbitrarily as the differential angles.
From this portfolio of differential angles, automobile paint manufacturers have selected the appropriate combination for their refinishing sections. As interest also grew in the OEM sector, automobile manufacturers defined their angle combinations, which they then set down as conditions of supply.
When interference pigments such as Iriodin were first introduced to the automotive world in the 1980s, the same measuring geometries were used to define and describe them, but without taking account of their optical characteristics. Only the newer types, such as XillaMaya or ChromaFlair forced users to look more carefully at the issue of optical characteristics, which in the world of physics are known as 'interference'. This refers to the selective reflection of rays of light. When these rays of light meet the surface of a pigment, some of the light is reflected back directly onto the surface. The remaining light passes through the highly graduated layer of refraction and is again partially reflected on the next layer (e.g. glimmer, mica). This part exits the pigment parallel to the first part, which causes interaction between the two known as interference. Due to the different paths that the two parts take, their wavelengths are pushed up against each other. If one wave peak then collides with the other wave peak, the resulting wave is accentuated. It weakens accordingly if a wave peak collides with a wave trough. This selection is known as interference. The resulting color is mainly dependent on the materials' refraction index, the thickness of the layer and the angle of incident light. The two first components can only be defined when the pigments are being manufactured. Only the latter component, the dependence of the angle of incident light, can be influenced by the user and changed.
Using transparent interference pigments, it can be demonstrated that interference can be documented up to 20° from the glancing angle. The area between 20° and 30° describes the transition from interference to the scattering of an effect pigment. The measuring results at differential geometries of 45°, 75° and 110° are therefore primarily influenced by a color's absorbing and scattering component.
The American standardization body ASTM published its "Standard Practice ..." E2539 in 2008. This divides the geometries into two groups: One group encompasses the geometries that must be used to measure aluminum pigments and corresponding applications. They are termed "aspecular" and are based on the relationship between differential angles to the glancing angle. Geometries that lie between the incident light and the corresponding glancing angle are given a positive mathematical sign. Differential angles on the side of the glancing angle that lies opposite to the incident light are given a negative mathematical sign. Positive angles can also be termed "cis" angles, and negative ones as "trans" angles.
While the measurements are performed for the first group with fixed illumination and varying differential angles, the second group's interference geometries are defined with varying angles of illumination and a fixed differential angle. However only a few measuring instruments have two or more sources of illumination for measuring interference. Newer, portable measuring equipment uses the -15° differential angle. It allows metallics and silver-white interference pigments to be distinguished from colorful interference pigments and their applications.


Measurement Geometries

For many users, the angle specifications on the measuring instruments are often hard to comprehend. Starting with an illumination angle of 45°, the portable devices measure at 15°, 25°, 45°, 75° and 110° from göloss. This lies -45° from the normal. The negative sign is physically not entirely accurate, since the optical law

angle of incidence = angle of reflection

holds true.
The aspecular geometries are calculated from gloss. As such, the specified angle of 15° actually means that the measurement takes place 15° from gloss and thus is conducted at -30°.

A new addition is the -15° geometry, which is measured behind gloss, in the "trans" position. Together with the +15° geometry, thus the "cis" position, the reflection curves can be used to analyze whether this is a coating formulation with color interference pigments or with white interference- or aluminum pigments.

Interference pigments - and with them, pigmented paints or plastics as well - can only be measured at an angle close to gloss. A reversal from the reflection color to the transmittance color takes place in the area between 20° - 30° from gloss. In simple terms, this means that the interference color most heavily influences the total color impression near gloss, while the absorbing portions determine the total color impression further from gloss.
This example shows pearl green on a gray background. The form of the reflection curve switches between 25° and 45°: That is the switch from the reflection to the transmittance.

The law of interference shows the dependency on the angle of the illumination: The flatter an illumination is, the more the color shifts towards the short wavelength. In this chart, the interference line connects the measuring points at different illumination angles. The gray line shows the values that are measured with the portable instruments.


Tactical Aspects for creating OEM Paints

Coating formulations of current OEM series paints generally consist of three different pigment types: Colored pigments that partially absorb incident light and scatter the rest in all directions, aluminum pigments that directly reflect light, and interference pigments that selectively reflect the light.
The present challenge consists of finding a way to combine these three types in a skillful manner. Should the colored pigments and with that, the scattering portions, be in the foreground? Or should, for example, the sparkle impression of the series paint be given a special tone and characteristic? In creating a modern OEM color, knowledge about the angle-dependent effects is important: Current portable measuring instruments are not entirely adequate for meeting the physical demands of measuring interference effects. With visual observation, geometries that also do not describe interference effects are often captured in a window or in a light booth.


Red Sparkle

XillaMaya pigments, especially XillaMaya Crystal Silver, are characterized by the special effect caused by their sparkle. This effect is not physical, but rather defined as a perception. Various companies and institutions have joined together to form a network called "Red Sparkle" in order to conduct research and exchange research results. ASTM (American Society for Testing and Materials) - the standardization committee that is America's equivalent to DIN, the German Institute for Standardization - established the topic of "Sparkle" as a task group.


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Contact                       deutsch english chinese espanol

Werner Rudolf Cramer
Hafenweg 22
48155 Münster
Germany
T +49-172-2366667

e-mail:
info (bei) wrcramer [punkt] de


Publications 2017

Eines für alle - Mischsysteme im Einsatz
DfwG-Report 2/2017

Kein blasser Schimmer
Kunststoffe 07/2017

Autolack: Wie Deutschland die Farbe verlor
www.farbeundlack.de 05/2017

以干涉顏料對彩色與灰色底漆進行測試對比的研究(下)
Coloured versus Grey Undercoats - Trials with Interference Colours (Part 2)
CCJ 5/2017

以干涉顏料對彩色與灰色底漆進行測試對比的研究(上)
Coloured versus Grey Undercoats - Trials with Interference Colours (Part 1)
CCJ 3/2017

Undercover influences
European Coatings Journal 05/2017
www.european-coatings.com

Buntes in Vergangenheit und Moderne
Fahrzeug + Karosserie 05/2017

Die Mischung macht's
Fahrzeug + Karosserie 05/2017

Lackierfehler - und wie sie sich vermeiden lassen
Fahrzeug + Karosserie 05/2017

Welcher Füller darf's denn sein?
Fahrzeug + Karosserie 05/2017

Livestream 2017/03/08
Farbe und Lack, Vincentz-Verlag

Im Untergrund steckt der Einfluss
Farbe und Lack 03/2017

Hidden Secrets of Effect Pigments
Paint & Coatings Industry 01/2017


Publications 2016

Farben und Mischlacke
Fahrzeug + Karosserie 12/2016

Farbe, nichts als Farbe?
DfwG-Report 3/2016

干涉着色剂和多色着色剂的有效使用
Paint & Coatings Industry 中文版 2016年11月

The Effective Use of Interference and Polychromatic Colorants
Paint & Coatings Industry 09/2016

Matt soll matt bleiben
autofachmann 08/2016

Great-looking thanks to interference pigments
European Coatings Journal 06/2016
www.european-coatings.com

干涉颜料与多彩色颜料的有效利用
www.chinacoatings.com.cn 06/2016

Matt soll matt bleiben
kfz-betrieb 16/2016

Veränderungen in kleinen Schritten
Fahrzeug + Karosserie 04/2016

Rainbows made to order
European Coatings Journal 04/2016

夢幻色彩創造的八個黃金法則
Eight Golden Rules for a Fantastic Colour Creation
CCJ 3/2016

Jenseits des Regenbogens
Farbe und Lack 03/2016

Formulating Excellent Automotive Effects
European Coatings Journal 01/2016

Das 1x1 der Farbkreation
Farbe und Lack 01/2016


Publications 2015

Farben und Mischlacke
Fahrzeug + Karosserie 12/2015

Effektheischend und bunt
Farbe und Lack 11/2015

Wenig Neues in Sicht
Fahrzeug + Karosserie 10/2015

Die Mattigkeit und ihre Folgen
Fahrzeug + Karosserie 4/2015

Mal so und mal so
Fahrzeug + Karosserie 2/2015

Aus meiner Sicht
Fahrzeug + Karosserie 1/2015

Weniger Bunt, mehr Weiß auf deutschen Straßen
Farbe und Lack 1/2015


Publications 2014

Wenn Farben fehlen
Fahrzeug + Karosserie 12/2014

Was hinterm Farbwunsch steckt
Fahrzeug + Karosserie 11/2014

Immer noch keine Bewegung
Fahrzeug + Karosserie 08/2014

Reparaturlackierung Teil4
Fahrzeug + Karosserie 08/2014

Wem gehört das Rot nun wirklich?
Fahrzeug + Karosserie 07/2014

Effektpower auf neuer Basis
Fahrzeug + Karosserie 06/2014

Farbenwelt und Mischsysteme
Fahrzeug + Karosserie 05/2014

So sieht's farblich aus auf den Strassen
fml 05/2014

Alles wie bisher oder?
Fahrzeug + Karosserie 03/2014

Reparaturlackierung Teil3
Fahrzeug + Karosserie 02/2014


2013 Publications

Farben und Mischlacke
Fahrzeug + Karosserie 12/2013

Reparaturlackierung Teil1
Fahrzeug + Karosserie 10/2013

Nichts Neues von der Straße
Fahrzeug + Karosserie 9/2013

Mattlackierungen beurteilen
Fahrzeug + Karosserie 5/2013

Dabei zwei neue Farben kreiiert
Fahrzeug + Karosserie 4/2013

Nicht mehr Farbe im Jahr 2012
Fahrzeug + Karosserie 2/2013

Reparaturlackierung Teil4
Fahrzeug + Karosserie 2/2013

Mix and match
European Coatings Journal 1/2013

Strategisches Farbdesign
Farbe und Lack 1/2013

Und somit deutlich schneller
Fahrzeug + Karosserie 1/2013


2012 Publications

Visuelle und instrumentelle Geometrien der Farbabmusterung
DfwG-Report 3/2012

Warum Farben so schön sind!
Fahrzeug + Karosserie 11/2012

Reparaturlackierung Teil3
Fahrzeug + Karosserie 09/2012

Den eigenen Farbton schaffen
Fahrzeug + Karosserie 09/2012

Reparaturhersteller mittendrin
Fahrzeug + Karosserie 09/2012

Den Geheimnissen der Lackkunst auf der Spur
Phänomen Farbe 08/2012

顏色匹配中的 目測及儀器幾何條件— 為何使用者覺得顏色匹配困難?
China Coatings Journal July 2012

Effekte richtig verstehen
Fahrzeug + Karosserie 05/2012

Making Sense of Measurement Geometries for Multi-angle Spectrophotometers
Color Research and Application 04/2012

Color Diversity
Kunststoffe International 04/2012

Über die Vielfalt der Farben
Kunststoffe 04/2012

Es glitzert wie am Sternenhimmel
Fahrzeug + Karosserie 04/2012

Reflections on the right angle
European Coatings Journal 04/2012

干涉顏料的光學性能 ——其描述和表征的方法
China Coatings Journal March 2012

Farbiger oder grauer Füller
Fahrzeug + Karosserie 03/2012

Es graut so grau auf deutschen Straßen
Farbe + Lack 03/2012

Reparaturlackierung Teil1
Fahrzeug + Karosserie 03/2012

Es wird eintöniger auf deutschen Straßen
Fahrzeug + Karosserie 02/2012

Beurteilung und Abmusterung von Interferenzpigmenten
Farbe + Lack 01/2012

Optische Wirkung des Klarlackes
Fahrzeug + Karosserie 01/2012


My books


In this book, I outline and present a number of my works dealing with "automobile paint design". It contains notes and information about colors, color systems, paints, paint applications and airbrushing.



My first Windows book - 3 years after the purchase of my first Compaq PC.



My second Windows book - now about Windows 3.1



Airbrush book No.1



Airbrush book No.2



Airbrush book No.3 - the completely revised edition of Airbrushing book No. 1



This history book was written together with Ingo Röver, who was responsible for the corrections and the technical details.


Co-author of 21st edition of Brockhaus encyclopedia


Co-author of "Auto und Karosserie", 2015

All books are listed in the German National Library:


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Automobile Paint Design

I expanded my photo laboratory in the mid 1970s, when I developed successful recipes and processes to produce prints up to 40 x 50 cm in size directly from slides without inter-negatives. My specialties included film developments - color negative film and slides - as well as pseudo-solarizations in color.
I displayed color prints that I made out of pseudo-solarized film in 1976 at my first exhibition at the town hall in the city of Münster, Germany. This was followed by twelve more exhibitions (also in towns such as Orleans, France and Enschede, Netherland) with various motif groups.
My preoccupation with color photography (and with the laws of color) was a good basis for starting up with automobile paint design. Since the refinishing paint can no longer be recognized once damage to an automobile has been repaired (that's the prerequisite for a successful repair), I had the idea of making targeted use of refinishing paint to style vehicles.
I gave this styling and technique the name "Autolackdesign" (automobile painting design) and, at the end of the 1980s, I wrote a book about it under the same title.

Complete styling of my first Golf: I primed the car with a white primer, placed a white pearlescent paint on top of it and then added two layers of clear coat. I taped up the stripes on the transparent varnish, painted the surfaces with a shaded primer and then with the colored pearlescent paint. I then added up to eight coats of clear coat with some intermediate sanding to give the effect that all the color stripes appear to be embedded in glass. This work took almost three months to complete.

This "Sun King" was the first of three models: The first Sun King (to the right in the photo) had color stripes that started on the rear right corner of the roof and ran towards the front left side. The second "Sun King" (shown in the middle of the photo) had the "sun" on the right side of the car, such that the driver's side of this Sun King was white.
The third "Sun King" was the brightest. It had the sun at the bottom of the driver's side and the color stripes proceeded across the entire vehicle (to the left in the photo).


aurum magicum

At the end of the 1980s, I came up with the idea of using new combination pigments (interference pigments featuring mica carriers and titanium dioxide/iron oxide layering) to create a golden paint. I selected one of 12 trial batches and baptized it with the lovely Latin name "aurum magicum". Its color and brilliance put it ahead of all of the other gold paints.
When compared to a vehicle painted with real gold powder, all of the testers were of the opinion that it was my Golf that had the genuine gold. I had not only "invented" gold, but had also succeeded in creating pale gold and rose gold all in one.
Eventually I sold the license to manufacture "aurum magicum" to the Wuppertal coating manufacturer Herberts, which offered the paint color in the refinishing program featured by Standox.

Where the rainbow ends is where the "aurum magicum" begins!


Tailor-Made OEM-colors

People should talk about paints and be able to recognize them! With this in mind, I created three OEM series paints for Volkswagen at the end the 1980s: "Golf Green" was and is the most noticeable series paint color, since its maximum reflection lies at the same wavelength as the maximum reflection of the sensitivity of our human eyes. "Golf Red" is the reddest shade of red in the series. "Golf Blue" completes the threesome.

"Mars Red" is on the left-hand side of the picture and is more yellow than "Golf Red", while "Verkehrs Purple" to the right is more blue than "Golf Red", which is the reddest red!
And where is the yellow in this trio? Stylistically speaking, a strong yellow would not fit well with these three Golf colors. And there's no dark yellow to be seen. Brown and ocher are not dark yellow colors, but they are often suggested as alternatives. As such, we stuck with the creation of these three "Golf colors"!


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