COLOUR MILL, a machine used in mixing and grinding paints. Its history may be traced back to the time when man first discovered that paint was made more tractable, and con sequently furnished a more beautiful surface, by thoroughly grind ing the contents. He secured two flat stones, placed the paint on the upper surface of the bottom stone, and milled it by rotat ing the top stone by hand. This method was slow and tiresome, and finally the principle was applied to a sort of gristmill type of which our present mills are a direct descendant.
Colour mills, or paint mills, fall into two general classifications : (I) those designed to grind or pulverize dry colours or dry paints, (2) those designed to grind paste paints and ready-mixed or liquid colours. The dry colour mills are divided into three groups: (I) The ball mill, which consists of a large cylinder made of cast iron, steel or bronze, and contains a quantity of balls, of similar metal, which pulverize the colours as the cylinder rotates; (2) The buhrstone mill, which is similar to the old-fashioned gristmill; (3) The disintegrator, which powders the dry colour by forcing it through closely set steel discs revolving at a tremen dous speed. This is the most modern type of dry colour mill.
It is necessary to grind paint thoroughly in order to "wet" each pigment particle with the so-called paint vehicle, to break up the agglomerates of pigment particles, and to expel the occluded air. In the case of the fine oil colours, artists' colours and inks, the pigment particle itself is actually ground finer. Thus the desiratum of the grinding procedure is the creation of paints per fect in texture and supreme in beauty of colour.
The paste and ready-mixed paint mills are of five types: (I) the stone mill, (2) the roller mill, (3) the pebble mill, (4) the iron mill, (5) the colloid mill. The most widely used of these is the stone, or buhrstone, mill. It is made of two flat, round stones, which are usually cut from Virginia or North Carolina buhrstone, French buhrstone, or Esopus stone, which is softer than buhr stone. The top stone is stationary and has a hole or eye in its centre, the size of which depends on the size of the mill. The lower stone, which rotates, is solid and adjustable, which means that it can either be forced up hard against the top stone, or that any desired clearance between the two stones can be main tained. The paint to be ground is dropped through the eye of the top stone and a grinding action is accomplished by the rotation of the lower stone, which forces the paint between the grinding surfaces of the two stones.
Stone mills vary in size from 8 in. in diameter, for laboratory use, to 6 ft., although the sizes in general commercial use range from 15 to 36 inches. Some are water-cooled and others have no cooling device, and others are also made in "tandem form" which consists of two mills in one, for double grinding. Grooves about - in. deep are cut into the grinding surfaces of the stones in such a manner as to give to the paint a scissor-cutting action between the stationary and revolving stones. For producing the most beautiful and delicate colours, the water-cooled 15 or 20 in. stone mills are used, the paint being reground until, when tested, it is found to be absolutely speckless.
Roller mills are constructed with one, three, or five chilled steel rollers, the three-roller type being the most widely used. These mills grind the paint by pulling it between the closely set rollers. Printing inks and the finest of enamels are ground on this type of mill and in many cases colours are ground and reground several times in order to produce the finest possible texture. The pebble mill is constructed with a large cylinder holding 55% paint and 45% pebbles. By rotating the cylinder the pebbles fall through the paint and break up the agglomerates or lumps. This type of mill is generally used for grinding paints in the ready-mixed form, whereas stone or roller mills are generally used for grinding in paste form. The iron mill operates on the same principle as the stone mill, except that the grinding sur face is smaller and of iron. This type is practically obsolete as paint "grinders," but is still being used to "feed" stone mills. Colloid mills, which are the most recently developed, are high speed mills grinding by forcing the paint through the minute clearance formed by the swiftly revolving steel "rotor" and the stationary steel "stator." The faces of the "rotor" and "stator" are machined with such precision that they can be adjusted to form an exact clearance of z o0o in. throughout their entire circumference. This mill is more of an emulsifier than a grinder, and is not being used extensively in the paint trade.
(G. W. C.) is the term most frequently employed to designate an art which makes use of varying light or lights as its principal means of expression. The first mention of such an art was made in the eighteenth century. From very ancient times, however, certain analogies had been observed between colours and sounds and particularly between the principal colours of the rain bow and the seven notes of the diatonic scale. The analogy be tween colour harmony and sound harmony was remarked upon by Aristotle in his De Sensu, while in the sixteenth century Arcim boldo, a Milanese painter, invented a system of colour harmony based upon a colour scale analogous in its order to the musical scale.
That there was some mysterious fundamental relationship be tween colours and sounds was a natural assumption in an age which was given to philosophizing upon the "Music of the Spheres." No doubt Kepler's The Harmonies of the Universe considerably influenced Sir Isaac Newton, whose sponsorship of the analogy gave it an authority which it has continued to possess to this day. Newton was struck by an analogy between the relative spaces occupied by the principal colours of the spectrum and the ratios of the notes of the diatonic scale, but as this observation depended entirely on the deviation of the particular prism he employed his conclusions were inaccurate, and it is probable that he himself later realized the nature of his mistake. Without question, however, his arbitrary division of the spectrum into seven principal colours has misled numberless colourists and it was not until late in the nineteenth century that it was proposed to develop an art of light entirely independent of the art of music.
The undulatory theory of light first propounded by Dr. Thomas Young in the Bakerian lecture before the Royal Society in 1801, and later incorporated into the general theory of electromagnetism in the hands of Clerk Maxwell and others, provided a new mathe matical foundation upon which the indefatigable analogists might once more erect their specious systems. The measurement of the wave lengths of visible radiation, the curious fact that the fre quency limits of visible radiation lie within the approximate compass of one octave, the fundamental similarity of the physical behaviour of electric waves and that of mechanical sound waves (namely, the similar laws of reflection, refraction, interference, etc.) all contributed towards an increasing confidence in the intimate correspondence between the two groups of phenomena. Only such great physicists as Helmholtz seemed to be able to per ceive the deep divergences between the two and to refer at last to the weakest point in the argument of the analogists, namely, to the radically different construction and characteristic response to stimuli of the two organs of sense involved, the eye and the ear.
Louis Bertrand Castel (1688-1757) was probably the first to propose an art of colour-music. Born at Montpellier, November I I, 1638, he became a Jesuit and was recognised as one of the most eminent mathematicians of his day. He first describes his La Musique en Couleurs in I720. Esprits, Saillies et Singularites du Pere Castel, published after his death in 1763, contains a chap ter, "Clavessin pour les Yeux," in which Castel states his general theory of colour-music, and describes a colour clavessin so con structed that the keys not only actuated the tongues for pluck ing the strings but also revealed certain transparent coloured tapes. Presumably it was his intention to place sources of light behind these.
Castel pursued his experiments with immense enthusiasm and wrote as intelligently about the subject as anyone ever has, but he was inevitably scorned by his contemporaries and almost for gotten by those who followed him. The fact remains that if any thing ever comes of colour-music, Castel will hold the position of the great pioneer who first explored the ground. He is the Giotto or Guido d'Arezzo of colour-music.
D. D. Jameson wrote a singular little pamphlet on colour music in 1844. He proposed a notation and gives examples. Ap parently he constructed an instrument of some kind and gave demonstrations. He employed glass containers filled with coloured liquids and projected light through these filters into a room lined with tin plates. Mechanically controlled shutters were used.
A prophetic passage occurs in a book called Music and Morals, by the Rev. H. R. Haweis (I875)—"And here I will express my conviction that a colour-art exactly analogous to the Sound-art of music is possible. . . . Nor do I see why it should not equal any in the splendour of its results and variety of its applications." Bainbridge Bishop of Essex County, New York State, having read Chevreul and Field, built (1877), a projection instrument which formed part of a house organ, by means of which he could blend colours on a small screen simultaneously with the playing of music, by attaching levers and shutters to the keys and direct ing first daylight and later the light from an electric arc through coloured glass.
William Schooling in an article in the Nineteenth Century (July, 1895), described an art of colour-music on the lines of the sound analogy, and proposed to use various vacuum-tubes, with intensity control in conjunction with a keyboard. This article was written in In the same year Professor Alexander Wallace Rimington (1854-1918) had independently conceived the idea of a colour organ which he patented and constructed. It was completed in 1893 and he gave a private demonstration of its powers at the old St. James's Hall, London, on June 6th, 1895. A complete account of his theories and experiments, and of the colour-organ may be found in his book Colour-Music: The Art of Mobile Colour (191I).
The project was next considered by Louis Favre, in his La. Musique des Couleurs et les Musiques de l'Avenir (I goo) . In the same year E. G. Lind, F.A.I.A., discussed a music-colour system and a projection instrument in The Music of Color and the Number Seven.
Mary HaHock Greenewalt, an American pianist, is one of the ablest experimenters of the present time. Though not insisting on a combined art of light and sound, she has spent most of her labours in the attempt to achieve such an aesthetic unity and her many patents and instruments are directed mainly to this end.
Thomas Wilfred, born in Denmark in 1889, began experiment ing in i9o5 and is perhaps the most active of contemporary colour musicians. Proceeding on independent lines he has from the first refused to be misled by the sound analogy. In 1919 he completed his first important colour-projector in America, where he no,,v resides, and this he named "The Clavilux." He has given colour concerts throughout the United States, and during 1925 he gave concerts in Paris, London and Copenhagen. Wilfred's procedure is to project upon a screen an even flood of light into which he introduces fantastic figures which rhythmically move and at thc same time alter their form and colour.
In Australia, Alexander Burnett Hector has for some years ex perimented with various forms of colour-music. His first colour organ made use of ordinary incandescent lamps combined with Geissler and X-ray tubes. M. Luckiesh, an American illuminating engineer, has also given the subject considerable attention and has experimented with various instruments for the production of mobile colour effects.
Other experimenters have been M. Carol-Berard and M. Va lere Berneird in France and Leonard C. Taylor, Claude Bragdon and Adrian Bernard Klein in England. The last named has con structed an instrument embodying optical means for the produc tion of coloured light by prismatic dispersion, the addition of white light to monochromatic light, control over wave-length and luminous intensity. The projector possesses an electrically oper ated key-board and is well suited to experimental work in all forms of colour-music.
Before discussing the theoretical requirements for an art of colour-music brief reference should be made to the phenomenon of colour audition (synaesthesia), whereby many musicians associate different keys with different colours. One of the earliest scientific investigations of this phenomenon is that recorded by Francis Galton in his Inquiries into Human Faculty (1883).
The "coloured hearing" of Scriabin, the Russian composer, led him to compose his Prometheus, the Poem of Fire, for which he wrote an accompaniment of changing coloured light. It was per formed in Moscow in 191r, with a colour-projection apparatus which apparently failed to function, and some years later (March 20, 19r5), at Carnegie Hall, New York, with a "Clavier a Lu mieres," when, however, the results were not impressive.
Will colour-music as a means of expression ever be accorded the dignity of one of the great arts? At present it is impossible to say. Yet there seems no reason why the aesthetic enjoyment derived from the perception of the unity of a musical composition, its parts having unfolded in time, should not be aroused, equiva lently, by observation of the construction of the various colour motifs, of combinations of sequences, and of the logical develop ment of these, in a composition of light. The view is sometimes expressed that colour has little or no interest when it is divorced from form or familiar shape, but the literature of the subject is full of enthusiastic reports by those who have witnessed demon trations of colour-music.
A great physicist, Prof. Albert A. Michelson, referring to the colour effects familiar to those who use optical instruments has written in his Light Waves and their Uses (19°3), "Indeed, so strongly do these colour phenomena appeal to me that I venture to predict that in the not very distant future there may be a colour art analogous to the art of sound—a colour-music in which the performer seated before a literally chromatic scale, can play the colours of the spectrum in any succession or combination, flash ing on a screen all possible gradations of colour, simultaneously or in any desired succession, producing at will the most delicate and subtle modulations of light and colour, or the most gorgeous and startling contrasts and colour chords! It seems to me that we have here at least as great a possibility of rendering all the fancies, moods and emotions of the human mind as in the older art." BIBLIOGRAPHY.—L. B. Castel, Nouvelles Experiences d'Optique et Bibliography.—L. B. Castel, Nouvelles Experiences d'Optique et d'Acoustique (1734) and Esprits, Saillies, et Singularites du Pere Castel (1763) ; Hooper and A. Morley, Explanation of the Ocular Harpsichord (1757) ; Dr. Busby, Assimilation of Colours to Musical Sounds 0825); D. D. Jameson, Colour-Music (1844) ; M. L. Favre, La Musique des Couleurs (189o) ; A. W. Rimington, Colour-Music, the Art of Mobile Colour (i9u); M. Luckiesh, The Language of Color and Color and its Applications (1918) ; A. B. Klein, Colour Music, The Art of Light (with bibl.) (1926). (A. B. K.)