Which white paint has the highest albedo. Characteristics and methods of painting with zinc white. CMYK and RGB systems

The retina consists of two types of light-sensitive cells - rods and cones. During the day, in bright light, we perceive the visual picture and distinguish colors using cones. In low light, rods come into action, which are more sensitive to light, but do not perceive colors. That's why at dusk we see everything in gray color, and there is even a proverb “At night all cats are gray

Because there are two types of light-sensitive elements in the eye: cones and rods. Cones distinguish colors, but rods distinguish only the intensity of light, that is, they see everything in black and white. Cones are less sensitive to light than rods, so in low light they cannot see anything at all. The rods are very sensitive and react even to very weak light. That is why in semi-darkness we cannot distinguish colors, although we see contours. By the way, cones are mainly concentrated in the center of the visual field, and rods are at the edges. This explains the fact that our peripheral vision is also not very colorful, even in daylight. In addition, for the same reason, astronomers of past centuries tried to use peripheral vision when making observations: in the dark it is sharper than direct vision.

35. Is there such a thing as 100% white and 100% black? In what units is whiteness measured??

In scientific color science, the term “whiteness” is also used to evaluate the light qualities of a surface, which is especially important for the practice and theory of painting. The term “whiteness” in its content is close to the concepts of “brightness” and “lightness”, however, unlike the latter, it contains a connotation of qualitative characteristics and even, to some extent, aesthetic.

What is whiteness? Whitecharacterizes the perception of reflectivity. The more a surface reflects the light falling on it, the whiter it will be, and theoretically, an ideal white surface should be considered a surface that reflects all rays falling on it, but in practice such surfaces do not exist, just as there are no surfaces that would completely absorb the incident light. them light.

Let's start with the question, what color is the paper in school notebooks, albums, books?

You probably thought, what kind of an empty question is this? Of course white. That's right - white! Well, what kind of paint were the frame and window sill painted? Also white. Everything is correct! Now take a notebook sheet, a newspaper, several sheets from different albums for drawing and drawing, put them on the windowsill and carefully examine what color they are. It turns out that, being white, they are all different colors (it would be more correct to say different shades). One is white-gray, another is white-pink, the third is white-blue, etc. So which one is “pure white”?

In practice, we call surfaces that reflect different amounts of light white. For example, we rate chalk soil as white soil. But if you paint a square on it with zinc white, it will lose its whiteness, but if you then paint the inside of the square with white that has an even greater reflectivity, for example barite, then the first square will also partially lose its whiteness, although we will practically consider all three surfaces white .

It turns out that the concept of “whiteness is relative, but at the same time there is some kind of boundary from which we begin to consider the perceived surface to be no longer white.

The concept of whiteness can be expressed mathematically.

Attitude luminous flux reflected by the surface to the flow incident on it (in percentage) is called “ALBEDO” (from Latin albus - white)

ALBEDO(from Late Latin albedo - whiteness), a value characterizing the ability of a surface to reflect a flow of electromagnetic radiation or particles incident on it. Albedo is equal to the ratio of the reflected flux to the incident flux.

This relation for a given surface is basically preserved at different conditions illumination, and therefore whiteness is a more constant surface quality than lightness.

For white surfaces, the albedo will be 80 - 95%. The whiteness of various white substances can thus be expressed in terms of reflectance.

W. Ostwald gives the following table of the whiteness of various white materials.

Barium sulfate (barite white)	99%
Zinc white	94%
White lead	93%
Gypsum	90%
Fresh snow	90%
Paper	86%
Chalk	84%

In physics, a body that does not reflect light at all is calledabsolutely black. But the blackest surface we see will not be completely black from a physical point of view. Since it is visible, it reflects at least some amount of light and thus contains at least a negligible percentage of whiteness - just as a surface approaching ideal white can be said to contain at least a negligible percentage of blackness.

In scientific color science, the term “whiteness” is also used to assess the lightness qualities of a surface, which, in our opinion, has a particularly important for the practice and theory of painting. The term “whiteness” is close in content to the concepts of “brightness” and “lightness”, however, unlike the latter, it contains a shade qualitative characteristics and even to some extent aesthetic.

What is whiteness? R. Ivens explains this concept as follows: “If lightness characterizes the perception of brightness, then whiteness characterizes the perception of reflectivity.” The more a surface reflects the light falling on it, the whiter it will be, and theoretically, an ideal white surface should be considered a surface that reflects all rays falling on it; however, in practice such surfaces do not exist, just as there are no surfaces that would completely absorb the light incident on them. In practice, we call surfaces that reflect different amounts of light white. For example, we rate chalk soil as white soil, but it’s worth painting a square on it zinc white how it will lose its whiteness. If we then paint the inside of the square with white that has even greater reflectivity, for example barite, then the first square will also partially lose its whiteness, although we will practically consider all three surfaces white. It turns out that the concept of “whiteness” is relative, but at the same time there is some kind of boundary from which we begin to consider the perceived surface to be no longer white.

The concept of whiteness can be expressed mathematically. The ratio of the light flux reflected by a surface to the flux incident on it (in percentage) is called “albedo” (from Latin albus - white). This relationship for a given surface is generally maintained under different lighting conditions, and therefore whiteness is a more constant quality of a surface than lightness. For white surfaces, the albedo will be 80-95%. The whiteness of various white substances can thus be expressed in terms of their reflectivity. V. Ostwald gives the following table of the whiteness of various white materials:

Barium sulfate (barite white) - 99%
Zinc white – 94%
Lead white - 93%
Gypsum - 90%
Fresh snow - 90%
Paper - 86%
Chalk - 84%

A body that does not reflect light at all is called an absolute black body in physics. But the blackest surface we see will not be completely black from a physical point of view. Since it is visible, it reflects at least some amount of light and thus contains at least a negligible percentage of whiteness - just as a surface approaching ideal white can be said to contain at least a negligible percentage of blackness. We consider a surface to be practically black, in the perception of which details are indistinguishable due to the lack of physical stimulus. White and gray in nature have superficial qualities, and gray, the darker it is, to a lesser extent. Black is devoid of these qualities. Ivens defines the difference between white, gray and black as follows: “White is a phenomenon related entirely to the perception of surface; gray is the perception of the relative lightness of the surface, and black is the positive perception of the insufficiency of the stimulus to provide the proper level of vision.”

In the practice of painting, the concept of black is also very relative. The most black spot in painting it has some whiteness and color tone. Various black colors, which can be mistaken for extreme blackness, turn out to be so only when perceived in isolation; when compared with each other, they, in addition, always reveal different color shades. Van Gogh, for example, counted up to 27 different black colors from Frans Hals. We almost never encounter purely achromatic black. The color of black paint is the standard of black for the artist, and the experience he has acquired in perception makes it possible to correlate all other tones with this blackness.

White paints are used in painting, decoration, construction and Everyday life. Zinc and titanium whitewash have found application in all areas of artistic activity related to the creation of a paint layer on the surface of a product or canvas. In construction, white is used for painting surfaces and as a pigment for some water-soluble paints.

White paints and the history of their creation

Much earlier than the advent of zinc white, humanity learned to make lead white. This type of paint was known to the ancient Greeks and Romans. Lead white was used everywhere until the 19th century.

Due to the toxicity of lead-based white paint, humanity has not given up attempts to create alternatives. This is how zinc white was invented. But, having appeared in 1780, they did not become widespread due to the high cost of their production process, and only 60 years later relatively cheap zinc-based white paints were obtained.

Following this, titanium white was discovered in 1912. These paints first appeared in Norway. Titanium white differs from other white paints in that it is completely non-toxic and has good covering properties.

Thus, new titanium and zinc compositions have replaced lead white.

Characteristics of white paints

Zinc white goes on sale in the form of ready-made or thickly rubbed paints. Thickly ground materials must be diluted before use. oil varnish. Other thinners are not suitable for this purpose, since as a result the painted surface will acquire a yellowish tint.

For this material in pure form characteristic snow-white color with a bluish tint. The quality and whiteness of this material depends entirely on the raw materials from which the pigment was obtained. This product should be stored in closed, since it absorbs from environment moisture. Zinc white pigments do not ignite and do not deteriorate under the influence of microorganisms.

This coloring material has a lot of positive qualities:

Good resistance to direct sunlight.
High level of compatibility with many colors in the colorful palette.
Possibility of application in all areas of painting and decorative arts.
Low toxicity.

Zinc white has negative qualities:

takes a long time to dry;
have low hiding power;
the paint layer created by whitewash is prone to cracking;
require large consumption of oil solvents.

Thickly ground white is used to obtain colorful compositions for coating wooden, metal and plastered surfaces of walls and ceilings.

Lead white had a pure snow-white color that did not lose its brightness when exposed to sunlight. TO positive qualities These paints include:

plasticity, which allowed the paint to remain strong and not crumble, even if it became necessary to roll up the canvas;
good resistance to moisture;
ability to quick drying paint layer after application to the surface.

Lead white has disadvantages that have caused it to become less popular:

high toxicity;
not mixed with all paints;
Over time, the paint layer loses its brightness.

All these negative sides led to the fact that lead white is not used for industrial purposes.

Titanium white is advantageous because it:

create a matte and very durable surface;
able to withstand exposure to atmospheric moisture and direct rays of light;
have the highest brightness of all modern white paints.

Titanium compounds have one drawback: when dry, they create a brittle surface of the paint layer.

Alkyd paints were the latest to appear; they are the product of a complex chemical synthesis.

Application

Due to its high toxicity, lead white is not used in everyday life. To paint surfaces in order to isolate them from moisture, oil-based zinc white, alkyd and titanium compounds are used.

For painting plastered walls and ceilings, water-soluble paints based on zinc white are used. It should be noted that walls are now rarely painted white; most often this paint is used to cover the ceiling.

Sequence of painting work

The ceiling is painted as follows:

The first thing you need to do before you start painting works, is to put on safety glasses over your eyes, and gloves on your hands; you should also cover your hair with a scarf or cap (this is done in order to avoid paint dripping from the ceiling from getting into your eyes and hair).
It is necessary to provide air access to the room. After painting, the room should be well ventilated.
Clean the ceiling from layers of old cracked and falling off plaster, paint, dust, grease, and drips.
Apply new layers of plaster and level the ceiling. Painting is carried out only on a perfectly flat surface.
The putty surface is sanded with sandpaper until the ceiling reaches the desired smoothness.
The surface, which has increased absorption properties, is covered with two layers of drying oil. The primer layers are allowed to dry between coats.

Painting metal products with white paints

There are two industrial way applying whitewash of any kind to the surface metal products. The first of them assumes full immersion metal parts into a container containing zinc or titanium white (lead white is not used for industrial purposes).

The second method of industrial painting of a metal surface involves applying a paint layer of zinc, alkyd or titanium compositions to the entire area of the product using a spray gun. For this purpose, solvents are added to paints. required quantity, after which the coloring composition is filtered. Only after this can you begin to apply the paint coating.

In everyday life, painting is done using a roller or brush (cars cannot be painted in this way). Also for coloring household items do not use white lead.

Coloring materials must be stirred before use. If they thicken, you can add zinc white to natural drying oil or . Oil paints are diluted with white spirit, turpentine or a special solvent for oil paints(all this can be purchased in specialized stores that sell goods for artists).
Paints are applied to a primed surface.
High-quality painting can be achieved by applying two layers of paint.
A new layer of paint is applied only to a well-dried surface, otherwise the film formed by the previous layers will be damaged.
If lead white is used in artistic activities, it is necessary to take precautions and periodically ventilate the room.

White paints are used in everyday life more often than others.

This is due to the fact that they are mixed with other colors to create the necessary shades. It is important to remember that you should only combine materials that are created on the same basis.

Lightness of color- one of the main qualities of color, associated with the quantitative ratio of reflected light and color absorbed by the surface of an object. The level of lightness of colored objects is determined by comparing them with achromatic objects and identifying the degree to which they approach white, which reflects maximum light, and move away from black, which absorbs maximum light. ()

So far we have spoken mainly about the composition of incident and reflected light. The diversity and unity of the spectra make up physical basis diversity and unity of colors - red, blue, green, brown, white, gray, black. Naturally, we include in one class of phenomena both spectral colors and those close to them, and achromatic (“neutral”) colors and those close to achromatic. It's all colors different qualities, different colors, different depending on the spectral composition of the radiation.

But in addition to their composition, radiation differs in strength or, if we talk about the vast majority of natural (non-point) light sources, in brightness. Brightness- physical concept. In the sensation of color, brightness corresponds to lightness. The brightness of incident or reflected light is the physical basis of the lightness of the corresponding color.

But, we will be asked, are light and color the same thing? The Impressionists turned everything into light. Light is radiation. He belongs to space. Color belongs to the object. The sun emits light. The sky glows at dawn, the disk of the moon and the lamp glow. Objects usually do not glow; they are not sources of light. On the other hand, however, the impression of color is caused precisely by the radiation entering the eye, and, if we ignore the aftereffects of the color stimulus, only by them. Before us again is the same duality in the understanding of color, the same difficulty, only in special issue about the lightness of color.

In fact, the issue is resolved this way. We contrast color to light without realizing that The color of the object ultimately also radiates, but less brightly. This is not at all difficult to verify. The disk of the rising moon near the horizon does not glow at all through the evening haze. We perceive the pale purple light of the disk as a color. The nearby electric lights on the embankment at this time of twilight seem to us, on the contrary, to be emitting yellow light. However, the further away the lights are, the weaker their light and closer to orange. The farthest lanterns seem to be just spots of a pale reddish color. If a sheet of white paper is illuminated by a bright sheaf of light that also covers surrounding objects, we see White color. But if you illuminate just one sheet of paper with the same light, tearing it out from its surroundings with a sheaf of light, the sheet will seem to glow, emitting white light. In fact, a sheet of paper in both the first and second cases emits the same stream of light waves reflected from it. We perceive relatively weak radiation as color, strong radiation as light. The artist knows that color can only be made to glow by creating sufficient contrast. The difference between light and color has no other physical meaning than the one named. This difference becomes a qualitative difference in the realm of sensations, just as the difference between spectra becomes the difference between red, blue, yellow, green, and brown.

We always perceive powerful light streams as light. Such is the light of the sun, the light of the moon and the lamp, if the latter do not have to retreat before the light of the sun. We most often (though not always) perceive light fluxes reflected from objects as color. The first ones seem to fill the space. We associate the latter with the surface of an object, its material.

Thus, the idea of the play and unity of the colors of nature as the play and unity of radiation remains.

At the same time, the difference between light and color, between a luminous and a colored object indicates the existence of a new side in the diversity and unity of the colors of nature. On the following pages we will use the contrast, common among artists, between “color” (which, therefore, corresponds to the spectral composition of the radiation) and “tone” (lightness, “luminosity”, which corresponds to the brightness of the radiation).

How does nature enrich and harmonize its colors through the “power of tone”? Light falling on objects around us causes many gradations of tone (lightness). The first reason for differences in tone is the variety of colors of objects, that is, the ability of a substance to absorb light more or less strongly. The reflected radiation will be brighter and the object will be brighter, the less strongly the substance absorbs the light incident on it. The relationship between the illumination of an object and the brightness of the radiation reflected from it is called “albedo”.

The albedo of white paper is approximately 0.8. The albedo of titanium white powder is about 0.9. Albedo does not change with changes in lighting and, as can be seen from a comparison with what was said above, constitutes the physical basis of what could be called the lightness of an object color. We see object lightness, and not just remember or know. This is taught by all our subject experience, everyday human practice. If of two objects the light one is in the shadow and the dark one is in the light, we can still, in many cases, correctly answer the question of which of them is lighter in color.

But we also see differences in tone caused by an objective difference in the brightness of the reflected radiation, and this latter is associated not only with the color of objects, but also with different illumination. Some objects are illuminated, while others are cast in shadow. The space is divided by light and shadow. Different planes of an object are illuminated more or less depending on their position relative to the light source. Light and shadow shape the shape of an object. In this regard, artists conventionally distinguish between “light”, “halftone” (or penumbra) and “shadow” (This division of chiaroscuro is a typical choice by the artist of the main thing in accordance with the task and method of work adopted at one time in the academic school).

However, we also see continuous transitions of tone from light to shadow and jumps in tone. In all these cases, we are no longer talking about objective lightness, but about tone as the visible brightness of reflected radiation. This also includes gradations of tone associated with space and spatial plans. Let us remember a row of lanterns stretching into the distance. The distant lights do not light up. Let's remember the smoothing out of tonal differences in distant plans compared to near ones. Throughout this we mean tone as the apparent brightness of the radiation. Lighting not only causes gradations of tone strength, entering into a complex interaction with objective lightness, but also unifies colors by tone, subordinating them to a general tone. The overall tone is a direct consequence of the overall illumination.

The general tone and illumination vary within very large limits, not only depending on whether we are in an open field, on a narrow street or indoors, not only depending on the weather, time of day, but also on a number of other reasons, for example, on the time year, from geographical latitude. The illumination of the sky by diffuse light at the latitude of Leningrad at one o'clock in the afternoon in January is 5 times less than the illumination at the same time of day in June and is equal to the illumination by diffuse light of the sky on a June evening (at 7 o'clock in the evening). Straight sunlight increases the illumination on a June afternoon by another 5-6 times. We certainly notice a difference in the overall illumination. A thundercloud has arrived, and we say: “It’s getting dark.” But the eye quickly gets used to the changed illumination. Its specificity is smoothed out.

In the room at daylight the illumination sufficient for reading a book is approximately 50 times less than the illumination of the diffused light of the sky in January at one o'clock in the afternoon. And indeed, the snow blinds us from the first minutes when we leave the room onto the street. However, we get so used to it room lighting that a still life placed in a room on a table may be painted by the artist in almost the same light colors as a still life placed in a garden in the diffused light of the sky. What can we say about dark interiors, depicted in not at all dark paintings by Adrian van Ostade, about the illumination of candles in Rembrandt’s “Descent from the Cross”?

Illumination is a powerful source of tonal unification. It creates a range of lightness of a given piece and the state of nature. It increases and decreases the number of visible lightness, sometimes causing many sharp differences, sometimes leading objects into color indistinguishability.

In color science lightness(IN) expressed in nits(nt) and for surfaces with diffuse reflection at the same conditions lighting estimated by reflection coefficient(R, %).

By lightness, you can compare any colors: achromatic with achromatic, chromatic with chromatic, chromatic with achromatic.

Light differences are inherent even in spectral colors. Among them, the lightest are yellow, the darkest are blue and violet. For achromatic colors, lightness is the only characteristic (except for texture).

On the lightness scale, the lightest is white, the darkest is black. Between them lies a gradation of pure gray. It is practically impossible to obtain pure gray colors by simply mixing black pigment with white. Such a mixture always produces a bluish-gray color. This deficiency is eliminated with small additions of golden ocher or natural umber.

White color is almost always present in the interior. This is the color of the ceiling, window frames and slopes, door leaves, walls in rooms that require special cleanliness, and sometimes even floors.

Big specific gravity White in the color scheme of the interior actively increases the illumination of the latter, helps to identify the finest shades of chromatic colors.

Black color is used relatively rarely and in small doses, as it depresses the psyche and has a gloomy symbolic meaning and, most importantly, reduces the illumination of the room. However, sometimes black color is given to large areas, using special techniques to neutralize its negative features. In modern interiors, it is still more often used on small surfaces to create strong contrast or to reveal the purity of chromatic colors.

Gray colors of varying degrees of lightness are used very often; the history of architecture knows many examples of their surprisingly effective use. They are especially desirable when it is necessary to reveal subtle plasticity, emphasize the sculptural nature of architectural forms, focus attention on surface modeling, and create a light-shadow accent instead of a color one.

Even in those frequent cases when the interior was designed in one achromatic color - white or silver-gray, but with developed plasticity of forms, the lightness was modeled by the “work” of light and shadow. The single-color achromatic composition was extremely enriched by the use of various finishing materials and textures. If it contained accent color in the form of a small spot, it gave it special effectiveness. In the architecture of classicism, this technique was often preferred to polychrome.

However, lightness is no less significant in chromatic compositions. Knowing how to see lightness ratios, it is easier to understand the characteristics of colors.

Chromatic compositions can be one-color if they are based on a single-tone row with different amounts gradations in lightness - a pure series in lightness, or multi-colored with different lightness of colors.

There is a technique when chiaroscuro defects are corrected by varying the lightness of the color. For example, a wall with light openings is made significantly lighter than the other walls to soften the sharp contrast of the heavily shaded partitions.

The gradation of lightness, as well as color tone, illusorily changes the spatial characteristics of the interior, increasing or decreasing, lightening or weighting, highlighting or masking architectural forms, giving the interior an emotional coloring.

The correct choice of lightness of enclosing surfaces is especially important if the interior needs precise differences in shades of color tones or saturation, or an increase in the level of illumination. For example, two medium-light, highly saturated complementary colors cause a ripple effect in the eyes. To avoid this drawback, you need to choose the optimal light of two interacting colors.

Lightness like important factor psychophysiological effects of color on humans, the first among others color characteristics received scientific justification and was recorded as a mandatory standard for the design of building interiors for various purposes. Lightness actively influences the degree of color sensation Q.

Lightness scale- this is an achromatic equal range from white to black with a varying number of gray shades, the visual distinction of which depends primarily on lighting conditions and the lightness of the background. The limit of the visual ability to distinguish steps in lightness is about 300 transitions. For practical purposes, the gray scale of 24 levels, developed by B. M. Teplov at the Institute of Psychology in Moscow, is quite sufficient. ()

Especially for ladies!

Lightness scale natural shades hair.

Many hair dye manufacturers introduce a special lightness scale for natural hair shades. Such a scale is necessary for: 1) classifying tone maps and creating a system for indexing color tones, 2) to determine the required degree of preliminary lightening of hair before using the corresponding coloring preparation, 3) to develop recommendations for correct selection coloring preparations for a specific type of original hair. Typically, the lightness scale is selected in a rather arbitrary manner, by dividing the entire lightness range from “black” to “white” into 10 ranges. This system seems quite convenient and is well received by hair dye consumers and hairdressers.

To introduce certainty and the ability to quantitatively characterize the original shades, we propose to carry out such a division in accordance with the value of the lightness coordinate L in the CIELAB system discussed above. Taking into account the high achromaticity of natural shades, such a system characterizes the original hair quite well. In accordance with this, lightness #1 is assigned to “black” hair, for which the measured L value is 5-10 units. Dark brown hair is assigned the 2nd lightness with a value of L=10-20. You can arrange all other hair types in a similar way. Wherein White hair, which are not pigmented and therefore achromatic, according to this system fall into the 10th lightness, for which L = 90-100. An example of such a lightness scale is shown in Fig.:

Lightness scale of initial hair shades, correlated with the results of studying diffuse reflectance spectra. The ordinate axis shows lightness L in Lab units, the abscissa axis shows the Kubelka-Munk function (f) associated with melanin concentration.

Vertical arrows indicate changes in lightness as a result of peroxide lightening (blondening): I - lightening of black hair by 4 tones, II - lightening of dark brown hair by 4 tones resulting in light brown hair, III - lightening of dark brown hair to light brown by 2.5 tones, IV - light brown to light blond by 1 tone.

It should be noted that the names of the types themselves natural hair, as well as their color nuances, can, apparently, be chosen quite arbitrarily by manufacturers or developers, taking into account the peculiarities of product promotion, as well as regional or national characteristics of hair color.

Names of individual colors for the proposed scheme for creating color names

That's enough for today. Note that the concept of lightness in English-language colorism is expressed in terms brightness, lightness, value.

In scientific color science, the term “whiteness” is also used to assess the lightness qualities of a surface, which, in our opinion, is of particular importance for the practice and theory of painting. The term “whiteness” in its content is close to the concepts of “brightness” and “lightness”, however, unlike the latter, it contains a connotation of a qualitative characteristic and even, to some extent, aesthetic.

What is whiteness? R. Ivens explains this concept as follows: “If lightness characterizes the perception of brightness, then whiteness characterizes the perception of reflectivity.” The more a surface reflects the light falling on it, the whiter it will be, and theoretically, an ideal white surface should be considered a surface that reflects all rays falling on it; however, in practice such surfaces do not exist, just as there are no surfaces that would completely absorb the light incident on them. In practice, we call surfaces that reflect different amounts of light white. For example, we rate chalk soil as white soil, but as soon as you paint a square on it with zinc white, it will lose its whiteness. If we then paint the inside of the square with white that has even greater reflectivity, for example barite, then the first square will also partially lose its whiteness, although we will practically consider all three surfaces white. It turns out that the concept of “whiteness” is relative, but at the same time there is some kind of boundary from which we begin to consider the perceived surface to be no longer white.

Barium sulfate (barite white) – 99%

Zinc white – 94%

Lead white – 93%

Gypsum – 90%

Fresh snow – 90%

Paper – 86%

In the practice of painting, the concept of black is also very relative. The blackest spot in a painting has some whiteness and color tone. Various black colors, which can be mistaken for extreme blackness, turn out to be so only when perceived in isolation; when compared with each other, they, in addition, always reveal different color shades. Van Gogh, for example, counted up to 27 different black colors from Frans Hals. We almost never encounter purely achromatic black. The color of black paint is the standard of black for the artist, and the experience he has acquired in perception makes it possible to correlate all other tones with this blackness.