Field's Chromatography Part 2

The pigments liable to injury from _sulphuretted hydrogen_, &c., are notably those obtained from lead and copper; and that treacherous compound of iodine and mercury, known as pure scarlet.

Many colours are apt to change from the action of white _lead_ and other lead pigments, &c., princ.i.p.ally those which are altered by light and air.

Many, too, cannot safely come into contact with iron, or ferruginous pigments; especially the yellows of a.r.s.enic, the lakes of cochineal, and the blues and greens of copper. With these an iron palette knife is best avoided, one of ivory or horn being used instead. The latter, indeed, is preferable in all cases, several pigments being slightly affected by iron, cadmium yellow among the number.

Numerous colours are likewise injured by _lime_ and _fire_, and cannot therefore be employed in fresco, or enamel painting.

Of substances which may act deleteriously on colours, there remain the _vehicles and varnishes_ with which they are mixed. Many of these have been blamed, and often with justice, for their injurious effects on pigments. The reputation of the most permanent colour may be ruined, if the vehicle, &c., employed with it be untrustworthy. The presence of lead, for instance, in such materials renders them liable to be blackened by foul air, and by consequence the pigments used therewith.

Time produces in many cases a mellow and harmonious change in pictures, but occasionally alterations altogether unfavourable. To ensure the former and prevent the latter, the attention of the artist in the course of his colouring should be to the employment of such pigments and colours as are p.r.o.ne to adapt themselves, in changing, to the intended key of his colouring, and the right effect of his picture. Thus, if he design a cool effect, ultramarine has a tendency through time to predominate and aid the natural key of blue. He will, therefore, compromise the permanence of this effect, if in such case he employ a declining or changeable blue, or if he introduce such reds and yellows as have a tendency to warmth or foxiness, by which the colouring of many pictures has been destroyed. In a glowing or warm key, the case is in some measure reversed--not wholly so, for it is observable that those pictures have best preserved their colouring and harmony in which the blue has been most lasting, by the pigment counteracting the change of colour in the vehicle, and that suffusion of dusky yellow which time is wont to bestow upon pictures even of the best complexion.

Unless introduced and guaranteed by houses of acknowledged reputation, newly discovered pigments are to be used with caution. Good colours have ever been prized with so true an estimation of their value, that to produce such, after so many ages of research is no ordinary accomplishment. But too many resplendent pigments, fruits of the fecundity of modern chemistry, have been found deficient. The yellow and orange chromates of lead, for instance, withstanding as they do the action of the sunbeam, become by time, foul air, and the influence of other pigments, inferior to the ochres. So the dazzling scarlet of iodine and mercury must yield the palm of excellence to the more sober vermilion, being a chameleon colour, subject to the most sudden and opposite changes. And the blues of cobalt, as always tending to greenness and obscurity, cannot rank beside ultramarine.

We are far from a.s.serting, however, that all modern pigments are inferior, or that pigments should be looked upon with suspicion because they are modern. Several most valuable colours have lately claimed attention, notably the permanent transparent yellow called _Aureolin_.

Seeing that, until its introduction, a yellow combining transparency with a perfect stability was unknown to the palette, the importance of such an addition, so long wanted and wished for, cannot be overrated.

Equal in beauty and durability with the preceding, but possessing greater richness and depth, and of a semi-opacity, another yellow of the highest order merits regard, _Orient Yellow_, distinguished for its l.u.s.trous golden hue, resembling a bright Indian yellow. Dazzling in brilliancy, and absolute in permanency. _Cadmium Red_ next attracts notice. This new aspirant for artistic fame is a most vivid orange-scarlet, the latter colour predominating, of intense fire, but with no approach to rankness or harshness, yielding delicate pale washes, and blending happily with white in the formation of flesh tints.

With it may be coupled _Cadmium Orange_, a colour equally brilliant and stable, and equally without rankness or harshness, but of a true orange hue, admirably adapted for sunsets and the like. Last of all the fresh pigments of whose thorough durability there is _no_ doubt, comes the splendid _Viridian_, a green nothing but fire will change, and no mixture of blue and yellow will afford. Clear, bright, and transparent as the emerald, it rivals velvet in its soft gorgeous richness. With this and Aureolin a series of beautiful foliage tints may be formed, sparkling with suns.h.i.+ne, as it were.

Other colours there are which have been brought forward within the last few years, not possessing the absolute permanency of the five foregoing, but equal, or superior, to many formerly used. It were folly, therefore, and a silly conservatism on the part of the artist to limit himself to such pigments only as were employed by his forefathers, especially as their merits were often more than doubtful. New colours, it is true, have to be _learnt_, for each pigment has its own peculiar habitudes, chemical, physical, artistic; but if they be good and durable, no amount of time and study spent upon them is thrown away. To think less of the quality of one's materials than of the effects which can be produced with them is mistaken policy; and to be content with that quality when better can be had, shows no real love of art, but rather indolence and apathy.

Perhaps one reason why freshly introduced pigments have not as fair a chance as they are ent.i.tled to, is due to the fas.h.i.+on which prevails of exclaiming against the fugacity of modern colours. If their detractors would confine themselves to certain colours, there could be no denial; but to a.s.sert, as is often done, that the cause of modern pictures not standing is owing to modern pigments generally, is unjust. It is not the materials which should be blamed, but those who use them. The fact is, that the artist's knowledge has not increased in proportion to the greater variety of colours at his command. In the early periods of art, when the palette was chiefly confined to native pigments, the painter could not very well go wrong. Now-a-days but too many, wanting the skill of the old masters, seek to make amends for it by brilliancy of colouring: with imperfect knowledge of their materials the result is obvious. The palette, we admit, wants weeding; not only of the bad new colours, but of the bad old colours. This, however, must be a work of time, and depend, not upon the colourman--for where there is a demand there will be a supply--but upon the artists themselves. To this end an increased acquaintance with the properties of pigments is required, whereby they may be able to choose the fast from the fugitive. It may be fairly a.s.sumed that the painter will be a.s.sisted in his task by the progress of chemical science, which will doubtless add from time to time to the list of stable pigments. We have heard it remarked that there are too many colours already--to which we reply, there are not too many good colours, and scarcely can be. The more crowded the palette is with reliable pigments, the more likely are the worthless to be pushed from their places. In our opinion, there is ample room for fresh colours, provided they be durable; and we have as little sympathy with the stereotyped cry of there being too many, as with the fas.h.i.+onable unbelief in modern pigments. Certainly, the artist who seeks for permanence among the whites, reds, or blues, will not be troubled with a superfluity. Certainly, too, colours are as good as ever they were, and better--better made, better ground, better prepared for use. But, fast and fugitive, pigments are more numerous, and for that reason need more careful selection.

CHAPTER V.

ON THE GENERAL QUALITIES OF PIGMENTS.

The general attributes of a perfect pigment are beauty of colour, comprehending pureness and richness, brilliancy and intensity, delicacy and depth,--truth of hue--transparency or opacity, well-working, crispness, setting up, or keeping its place, and desiccation, or drying well. To all of these must be superadded _durability_ when used, a quality to which the health and vitality of a picture belong, and one so essential that all other properties put together without it are of no esteem with the artist who merits reputation. We have, therefore, given it a previous distinct consideration.

It must be observed that no pigment possesses all the foregoing qualifications in perfection, some being naturally at variance or opposed; nor is there any, perhaps, that cannot boast excellence in one or more of them.

_Beauty_ commonly comprises in the same pigment delicacy, purity, and brilliancy; or depth, richness, and intensity. Delicacy and depth in the beauty of colours are at variance in the production of all pigments, so that perfect success in producing the one is attended with more or less of failure in the other, and when they are united--as they occasionally are--it is with some sacrifice of both. Hence the judicious artist purveys for his palette at least two pigments of each colour, one eminent for delicate beauty, the other for richness and depth.

_Truth of hue_ is a relative quality in all colours, except the extreme primaries, in the relations of which, blue, being of nearest affinity to black or shade, has properly but one other relation, in which it inclines to red and becomes purple-blue: it is, therefore, faulty or false, when, tending to yellow, it becomes of a green hue. But red, which is of equal affinity to light and shade, has two relations, by one of which it verges upon blue and becomes a purple-red or crimson; and by the other it leans to yellow, and becomes an orange-red or scarlet, neither of which is individually false or discordant. Yet yellow, which is of nearest affinity to white or light, has strictly but one true relation, by which it inclines to red, and becomes a warm or orange yellow, for by uniting with blue it becomes a defective green-yellow.

The best example of true yellow in a pigment, tending neither to red nor blue, is furnished by _Aureolin_, alluded to in the last chapter. The secondary and tertiary colours, having all duplex relations, may incline without default to either of their relatives.

_Transparency_ is an essential property of all glazing pigments, and adds greatly to the value of dark or shading colours; indeed it is the prime quality upon which depth and darkness depend, as whiteness, or light, does upon opacity or reflecting power. _Opacity_ is, therefore, the antagonist of transparency, and qualifies pigments to cover in dead-colouring, or solid painting, as well as to combine with transparent colours in forming tints; and hence it is that semi-transparent pigments are suited in a mean degree both for dead colouring and for finis.h.i.+ng. As excellencies, therefore, transparency and opacity are relative only--the first being as indispensable to shade in all its gradations, as the latter is to light. With regard to transparent and opaque colours generally, it is worthy of attention in the practice of the oil-painter, that the best effects of the former are produced when they are used with a resinous varnish; as opaque pigments are best employed in oil, and the two become united with best effect in a mixture of these vehicles. The natural and artificial powers, or depth and brilliancy, of every colour lie within the extremes of black and white; hence it follows that the most powerful effects of transparent colours are obtained by glazing them over black and white. As, however, few transparent pigments have sufficient body, or tinging power for this, it is often necessary to glaze them over tints, or deep opaque colours of the required hues. There is a charm in transparent colours which frequently leads to an undue use thereof in glazing; but glazing, sc.u.mbling, and their combined process must be employed with discretion, according to the objects and effects of a picture.

_Working well_ is a quality which depends princ.i.p.ally upon fineness of texture, and what is called _body_ in colours; yet every pigment has its peculiarities in respect to working both in water and oil, and these must become matter of every artist's special experience. Some of the best pigments are most difficult of management, while some ineligible colours are rich in body and free in working. Accidental circ.u.mstances, however, may influence all pigments in these respects, according to the painter's particular mode of operation, and his vehicle; upon the affinities of colours with which depend their general faculties of working--such as keeping their place, crispness or setting up, and drying well. These latter, with other properties and accidents of pigments, will be particularly considered in treating of their individual characters; but it may be remarked that crispness or setting up, as well as keeping their place and form in which they are applied, are contrary to the nature of many pigments, and depend in painting with them upon a gelatinous mixture of their vehicle. For example, mastic and other resinous varnishes impart this texture to oils which have been rendered drying by the acetate, or sugar of lead:--simple water, also alb.u.men, and animal jelly made of glue and isingla.s.s, give the same quality to oils and colours; and bees-wax has a similar effect in pure oils. Whitelac varnish, and other spirit varnishes, rubbed into the colours on the palette likewise enable them to keep their place very effectually in most instances. This is important, because glazing cannot be performed except with a vehicle which keeps its place, or with pigments which lend this property to the vehicle, as some lakes and transparent colours do.

_Fineness of texture_ is produced by extreme grinding and levigation.

Pigments ground in water in the state of a thick paste, are miscible in oil and dry therein firmly; and in case of utility or necessity, any water-colour in cake, being rubbed off thick in water may be diffused in oil, the gum acting as a medium of union between the two. Thus, pigments which cannot otherwise be employed in oil, or varnish, may be forced into the service and add to the resources of the oil-painter, care being taken to use the palette-knife, if of steel, with caution.

_Desiccation or drying._ The well-known additions of the acetate, or sugar of lead, litharge, and sulphate of zinc, either mechanically ground, or in solution, for light colours; and j.a.panner's gold size, or oils boiled upon litharge, for lakes; or, in some cases, manganese and verdigris for dark colours, are resorted to when the pigments or vehicles are not sufficiently good dryers alone. It would be well if lead and copper could be banished from the list of siccatives altogether: a.s.suredly, no artist with any regard for the permanent texture of his work should employ them except in extreme cases, and in the smallest possible quant.i.ty. The best of pigments may be ruined by their injudicious use, and obtain a character for fugacity which they in no way deserve. It requires attention that an excess of dryer renders oil saponaceous, is inimical to drying, and is otherwise injurious. Some colours dry badly from not being sufficiently edulcorated or washed.

Sulphate of zinc, as a siccative, is less powerful than acetate of lead, but is far preferable in a chemical sense. It is supposed erroneously to set the colours running; which is not positively the case, though it will not retain those disposed to move, because it wants the property the acetate of lead possesses, of gelatinizing the mixture of oil and varnish. These two dryers should not be employed together, since they counteract and decompose each other, forming two new substances--acetate of zinc, which is a bad siccative, and sulphate of lead, which is insoluble and opaque. The inexperienced ought here to be guarded against the highly improper practice of some artists, who strew their pictures while wet with acetate of lead, or use that substance in some other mode, without grinding or solution; which, though it may promote present drying, will ultimately effloresce on the surface of the work, throw off the colour in sandy spots, and expose the paintings to peculiar risk from the damaging influence of impure air.

It is not always that ill drying is to be attributed to the pigments or vehicles, the states of the weather and atmosphere have great influence thereon. The direct rays of the sun are powerfully active in rendering oils and colours siccative, and were probably resorted to before dryers were--not always wisely--added to oils, particularly in the warm climate of Italy. The ground may also advance or r.e.t.a.r.d drying, because some pigments united by mixing or glazing, become either more or less siccative by their conjunction. Many other accidental circ.u.mstances may likewise affect drying; and among these none is to be more guarded against by the artist than the presence of soap and alkali, too often left in the was.h.i.+ng of his brushes, and which, besides other bad results, decompose and are decomposed by acetate of lead and most siccatives. In such cases desiccation is r.e.t.a.r.ded, streaks and patches are formed on the painting, and the odium of ill drying falls upon some unlucky pigment. To free brushes from this disadvantage, they should be cleansed with linseed oil and turpentine. Dryers should be added to colours only at the time of using them, because they exercise their drying property while chemically combining with the oils employed, during which the latter become thick or fatten. Too much of the siccative will, as before noticed, often r.e.t.a.r.d drying.

The various affinities of pigments occasion each to have its more or less appropriate dryer; and it would be a matter of useful experience if the habits of every colour in this respect were ascertained. It is probable that siccatives of less power generally than the compounds of lead and copper might come into use in particular cases, such as the oxides of manganese, to which umber and the Cappagh browns owe their drying quality.

To other good attributes of pigments, it would be well if we could in all cases add the property of being _innoxious_. As this, however, cannot be, and colours are by no means to be sacrificed on that account, cleanliness and avoiding the habit of putting the brush unnecessarily to the mouth, so common in water-painting, are sufficient guards against any possibly pernicious effects from the use of any pigment. No colour which is not imbibed by the stomach will in the slightest degree injure the health of the artist.

PART III.

ON COLOURS AND PIGMENTS INDIVIDUALLY.

CHAPTER VI.

ON COLOURS AND PIGMENTS INDIVIDUALLY.

Having briefly discussed the relations and attributes of colours and pigments generally, we come to their powers and properties individually--a subject pregnant with materials and of unlimited connexions, every substance in nature and art possessing colour, the first quality of pigments.

With regard to _colours_ individually, it is a general law of their relations, confirmed by nature and the impressions of sense, that those colours which lie nearest in nature to light have their greatest beauty in their lightest tints: and that those which tend similarly towards shade are most beautiful in their greatest depth or fulness, a rule of course applying to black and white particularly. Thus, the most beautiful yellow, like white, is that which is lightest and most vivid; blue is most beautiful when deep and rich; while red is of greatest beauty when of intermediate depth, or somewhat inclined to light; and their compounds partake of these relations. We speak here only of the individual beauty of colours, and not of that relative beauty by which every tint, hue, and shade of colour become pleasing, or otherwise according to s.p.a.ce, place, and reference; for this latter beauty belongs to the general nature and harmony of colours.

In respect to _pigments_ individually, it may be observed that--other things being equal--those pigments are the most beautiful which possess the most colour, whether they be light or dark, opaque or transparent, bright or subdued. There are some which exhibit all their colour at a glance: there are others that the more they are looked into the more colour they are found to have--containing, as they do, an amount of _latent colour_, not immediately apparent. Apart from the beauty which a wealth of colour imparts, those pigments imbued with it are, as a rule, the most permanent. And not unnaturally so, for the more colour there is present, the longer it takes to be affected, either by exposure or impure air. Colour within colour, therefore, not only lends charm to a pigment, but contributes to its safety.

There is often a vicious predilection of some artists in favour of a particular colour, from which many of our best colourists have not been totally free, and which arises from organic defect, or mental a.s.sociation. Such predilection is greatly to be guarded against by the colourist, who is every way surrounded by dangers. On the one hand, there is fear lest he fall into whiteness or chalkiness; on the other, into blackness or gloom: in front he may run into fire and foxiness, or he may slide backward into cold and leaden dulness: all of which are extremes he must avoid. There are also other important prejudices to which the eye is liable in regard to colours individually, that demand his particular attention. These are occasioned by the various specific powers of single colours acting on the eye according to their ma.s.ses and the activity of light, or the length of time they are viewed. By consequence, vision becomes over-stimulated, unequally exhausted, and endued, even before it is fatigued, with a spectrum which not only clouds the colour itself, but gives a false brilliancy by contrast to surrounding hues, so as totally or partially to throw the eye off its balance, and mislead the judgment. This derangement of the organ may be caused by a powerful tint on the palette, a ma.s.s of drapery, the colour of a wall, the light of a room, or other accidental circ.u.mstance; and the remedy is to refresh the eye with a new object--of nature, if possible--or to give it rest. The powers of colours in these respects, as well as of pigments individually, together with their reciprocal action and influence chemically, will be adverted to under their distinct heads.

The attention of the artist to the individual powers of pigments, although it may be of less concern than the attention to general effect in colouring, is by no means less necessary in practice. For he who would excel in colouring must study it from several points of view, in respect to the whole and the parts of a picture, as regards mind and body, and concerning itself alone. To this end, is needed a knowledge of his pigments individually.

If nature has arrayed herself in all the colours of the rainbow, she has not been n.i.g.g.ardly in offering man the materials wherewith to copy them.

The mineral, animal, vegetable kingdom--each helps him to realize, however faintly, her many manifold beauties: to give some idea, however slight, of that glorious flood of colour, which light lets loose upon the world. Metal, ore, earth, stone; root, plant, flower, fruit; beast, fish, insect--in turn aid the arduous task. The painter's box is a very museum of curiosities, from every part of the universe. For it, the mines yield their treasures, as well as the depths of the sea: to it come Arab camel, and English ox, cuttle-fish and crawling coccus: in it the Indian indigo lies next the madder of France, and the gaudy vermilion of China brightens the mummy of Egypt. Varied, indeed, are the sources whence we derive our pigments; and if they still leave much to desire, improvement is clearly manifest. Slowly but surely, year by year, we are advancing. With the growth of science, the exhaustless stores of creation, will there at last be attained--step by step, though it be--that summit of the artist's hopes, a perfect palette?

CHAPTER VII.

ON THE NEUTRAL, WHITE.

The term "colour" is equivocal when applied to the neutrals, yet the artist is bound to consider them as colours; for a thing cannot but be that of which it is composed, and neutrals are composed of, or comprehend, all colours.

With regard to colour, then, _white_ in a perfect state should be neutral in hue, and absolutely opaque; that white being the best which reflects light most brilliantly. This property in white is called _body_; by which in other pigments, especially those that are transparent, is meant _tingeing power_. White, besides its uses as a colour, is the instrument of light in painting, and compounds when pure with all colours, without changing their cla.s.s. Yet it dilutes and cools all colours except blue, which is specifically cold; and, though it does not change nor defile any colour, it is changed and defiled by all colours. This pureness of white, if it be not in some degree broken or tinged, will cast down or degrade every other colour in a picture, and itself become harsh and crude. Hence the lowness of tone which has been thought a necessity in painting, but is such only because our other colours do not approach to the purity of white. Had we all necessary colours thus relatively pure as white, colouring in painting might be carried up to the full brilliancy of nature; and, in fact, more progress has already been made in that respect, than the prejudice for dulness is disposed to tolerate.

Locally, white is the most advancing of all colours in a picture, and produces the effect of throwing others back in different degrees, according to their specific retiring and advancing powers. These latter, however, are not absolute qualities of colours, but depend on the relations of light and shade, which are variously appropriate to all colours. Hence it is that a white object rightly adapted, appears to detach, distribute, and put in keeping; as well as to give relief, decision, distinctness, and distance to every thing around it: hence, too, the use and requirement of a white or light object, in each separate group of a composition. White itself is advanced or brought forward, unless indeed white surround a dark object, in which case they retire together. In mixture, white communicates these properties to its tints, and harmonizes in conjunction with, or in opposition to all colours; but lies nearest in series to yellow, and remotest from blue, of which, next to black, it is the most thorough contrast. It is correlative with black, which is the opposite extreme of neutrality.