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damp and moisture, it is well adapted, with colours properly chosen, to situations in which paintings, executed in other modes of the art, or even in ordinary fresco, would not long endure.

As these materials, and others now in use, were either unknown or unemployed by the antient painters in fresco, their practice was necessarily limited to the pigments enumerated in the preceding table; but every art demands such a variation in practice, as adapts it to circumstances and the age in which it is exercised, without attention to which it may degenerate, or, at best, remain stationary, but cannot advance.

In point of durability, however, both as respects colours and texture, the frescos of the antient Egyptians (if they may be so called) have alone pretensions to the character of almost perpetual incorruptibility; in which respect fresco must have declined, at the same time that painting as an art advanced, even among the Greeks; while many of the earlier works of the moderns, founded on the basis of Grecian art, have nothing to boast of in this respect; and the "Last Judgment" of Michael Angelo, and many great performances, may be adduced as examples thereof; so that, aided by modern physics, we may hope not only the restoration, but improvement of this art.

Although differing exceedingly in their mechanical execution, the modes of fresco, distemper, and crayon painting agree in their chemical relations; so far, therefore, as respects colours and pigments, the foregoing remarks apply to these latter arts. In distemper painting, however, the carbonate of lime, or whitening employed as a basis, is less active than the pure lime of fresco. The vehicles of both modes are the same, and their practice is often combined in the same work: water is their common vehicle; and to give adhesion to the tints and colours in distemper painting, and make them keep their place, they are variously mixed with the size of glue (prepared commonly by dissolving about four ounces of glue in a gallon of water). Too much of the glue disposes the design to crack and peel from the ground; while, with too little, it is friable and deficient of strength. In some cases the glue may be abated, or altogether dispensed with, by employing plaster of Paris diluted and worked into the colours; by which they will acquire the consistency and appearance of oil paints, without destroying their limpidness, or allowing the colours to separate, while they will acquire a good surface, and keep their place in painting with sufficient strength, and without being liable to mildew,-to which animal glue is disposed, and to which milk, and other vehicles recommended in this mode, are also subject.

Of more difficult introduction in these modes of painting is bees'-wax, although it has been employed successfully in each of them, in the encaustic of the antients, &c.; the body colours of the moderns; and, with excellent effect, in crayons,-first, we believe, by the late Mr. Adam Buck. Wax is a most incorruptible substance, and communicates many of the qualities of oil-painting.

CHAP. XXIII.

ON VEHICLES AND VARNISHES.

How many fondly waste the studious hour
To seek in process what they want in power,
Till all in gums engross'd, macgilps, and oils,
The painter sinks amid the chemist's toils.

SHEE.

SINCE colours and pigments are liable to material influence, and changes of effect, from the liquids employed in painting for tempering, combining, distributing, and securing them on their grounds in the various modes of the art,—the powers and properties of vehicles and varnishes are of hardly less importance than those of colours themselves; they are therefore an essential branch of our subject, and an inquiry of interminable interest among artists. Vehicles are, indeed, among the chief materials and indispensable means of painting, and give names to its principal modes or genera, under the titles of painting in water, in oil, in varnish, &c.: we will consider them in reference to each.

Though originally few and simple, vehicles have been extremely diversified by composition and addition, suited to the various purposes and fancies of artists, so as to have become a subject of no mean extent and intricacy; to explicate which perfectly is as far from our hope as our intention, which is to treat of it in a general way, with such hints and remarks as have sprung from our own observation and experience, and may tend to improvement in practice.

It is observable that the colours of pigments bear out with effects differing according to the liquids with which they are combined, and the substances those liquids hold in solution, which in some instances obscure or

depress, and in others enliven or exalt the colours; in the first case by the tinge and opacity of the fluid; and in the latter, by its colourless transparency, and sometimes also much more so by a refractive power,—as in varnishes made of pure resinous substances, which have a very evident and peculiarly exalting effect upon colours, that continues when they are dry; because resins form a glossy transparent cement, while the media, formed by expressed oils, become horny, or semi-opaque. And this principle applies also to aqueous and spirituous vehicles in water-painting, according to the nature of the gums, or other substances they may hold in solution.

As the action of AQUEOUS LIQUIDS, and their solvends upon colours, is stronger and more immediate than that of oils and varnishes, it is of great importance to the water-colour painter that he should attend to the pureness of his water. He ought to use no other than distilled water; or, wanting this, he should use rain-water filtered, which is next in purity to distilled water. In all hard and impure waters, colours are disposed to separate and curdle, so that it is often impossible a clear flowing wash, or gradation of colour, should be obtained with them. Solution of gums, oxgall, &c. correct, without entirely overcoming these defects of the water; but they are often inconvenient, if not injurious: we recommend therefore to colourmen to keep distilled water ready for artists' use; or the latter may, if he pleases, procure it of the chemists, or use in its stead the distilled water of roses, or lavender, &c. which have no injurious effect upon colours, and recommend themselves by their agreeable scents; but then they must be the really distilled waters, and not the compounds sold as perfumes under their names.

GUM is a necessary addition to water to give pigments their requisite cohesion, and to attach the colours to the paper or ground on which they are applied, as well as to give them the property of bearing out to the eye, according to the intention of the artist; upon which, and upon the pigments used, depend the proportions of gum to be employed, gum being a constituent of some pigments, while others are of textures to require it in considerable quantity to give them proper tenacity,-qualities we have adverted to in speaking of individual pigments: as a general rule, however, the proportion of gum employed with a colour should be sufficient to prevent its abrasion, but not so much as to occasion its scaling or cracking, both of which are easily determined by trial upon paper.

Of GUMS, SENEGAL is the strongest and best suited to dark colours; but

GUM ARABIC is in general clearer and whiter, and thence is better adapted to the brighter and more delicate colours; these should be purified by solution in water, straining, and decanting, and should be used fresh or preserved by addition of alcohol.

TRAGACANTH is a strong colourless gum, soluble in hot water, and of excellent use when colours are required to lie flat, or not bear out with gloss, and also when a gelatinous texture of the vehicle is of use to preserve the touch of the pencil and prevent the flowing of some colours; for which purpose also solution of isinglass is available, and of greater power.

AMMONIAC, or Gum Ammoniac, is a gum-resin, soluble in spirit and in water, in the latter of which it forms a milky fluid that dries transparent: it has many properties which render it useful in water-painting, and is, we have found, superior to the gums in forming some colours into cakes, causing them to work off. It is avoided by insects, is very tenaceous, and affords a middle vehicle between oil and water, with some of the advantages of both.

A most excellent mucilage for water-painting may be made by diluting gradually clear size of ISINGLASs with boiling water, till, on becoming cold, it just flows and loses its gelatinous texture: in this liquid is then to be dissolved by gentle heat as much colourless gum Senegal, or Arabic, as it will conveniently take up.

The ingenious Mr. Robertson, of Worton, has employed isinglass in water-painting with the happiest effect, of which his well-known admirable copy of the "Bacchus and Ariadne" of Titian is sufficient evidence. This picture, as well as the original works of this gentleman, possess the full powers of oil-painting, with a permanence of tone not to be expected in oil; and being varnished with white lac varnish, may be considered as of extreme durability. His vehicle, for which the Society of Arts voted him a gold medal, may be prepared by suffering shreds of isinglass to imbibe cold water till thoroughly soft, and then dissolving them in boiling alcohol, in such proportions as will just produce a fluid compound when cold. Spirit of wine alone will, Mr. Robertson states, by boiling dissolve isinglass, which we presume is effected by the weakening of the spirit, as the more volatile portion becomes dissipated by the heat.

It has been an opinion of eminent judges in the art, that the Venetian painters—after a mode also ascribed to some of the great antient Greek artists-employed oils and varnishes only as preservatives and defences of

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