more difficult management; it is, therefore, a desideratum with the artist to form a macgilp of copal, which would stand up with the flimsy firmness of that of mastic; till which can be done he must be content to mix it as above; for linseed oil is essential to prevent its cracking. The mixture of copal varnish and linseed oil is best effected by the medium of oil of turpentine, and for this purpose heat is sometimes requisite: strong copal varnish and oil of turpentine in equal portions with one-sixth of drying oil mixed together, hot, afford this vehicle; and if about an eighth of pure bees'-wax be melted into it, it will enable the vehicle to keep its place in the manner of macgilp.

AMBER VARNISH has been more reputed in painting than it merits. The process by which it is prepared is the same as that of copal; but amber is more difficult of solution, is of a deeper colour than copal, and, owing to the succinic acid it contains, dries very slowly in solution. Amber of the palest colour is most easily dissolved, and at the same time affords the best varnish.

WHITE LAC VARNISH has hitherto been only partially used in painting, for which, its being a spirit varnish that requires a warm temperature and dries rapidly, and its repugnance to combine with oils, in permanent mixture, disqualifies it by rendering it difficultly manageable as a vehicle. It has, however, been introduced, by rubbing, into oil colours on the palette, with a view to the giving them permanence by cloathing them, and a crispness which makes them stand up and keep their place. Its extreme transparency, and the power with which it causes colours to bearout, have occasioned its successful introduction in the progress of a picture, to bring out and preserve the force and richness of deep colouring and shadows. To what more extensive use the ability and ingenuity of artists may apply it in oil-painting remains to be proved.

The principal recommendations of white lac, as a varnish, are the remarkable power and effect with which it brings out the colouring and design of a picture, and the permanence with which it so preserves them; it being neither subject to bloom, chill, nor crack, when skilfully and properly applied, according to the general rules for all varnishes, and those of spirit varnish in particular; the principal of which are a dry atmosphere and summer warmth of the apartment in which they are used. At a temperature of

not less than 60°, it dries in a second or two, and coat after coat, as it dries, may be applied with a broad soft camel-hair brush. This soon becomes harder and firmer than any other varnish, and entirely free from the tackiness by which they catch and retain the dust and floatings of the atmosphere, and from the opacity and discolourment by which varnishes ultimately obscure pictures on which they are applied; so that removing this varnish from a picture becomes an unnecessary operation, though this may be easily effected, if required, by the proper use of spirit of wine. This and all other spirit varnishes differ from those of fixed or expressed oils in this respect, that spirit and essential oil varnishes are dissoluble, and removable from pictures, by alcohol and essential oils, &c.; but fixed oil varnishes are insoluble by such means, or any other not injurious to the painting itself.

Lac varnish may be combined with mastic varnish, in small proportion, so as greatly to improve it; it may also be employed in the manner of other spirit varnishes in varnishing drawings, prints, &c., which have been previously sized with isinglass; and, being first thickened by setting it to evaporate in an open vessel in a warm place, it may be passed over miniatures, &c., without previous sizing, so as to give them much of the strength, force, and durability of oil-paintings; but in all these cases it should be used in warm dry weather, or near a fire.

mer.

Upon comparing the qualities of the varnishes of mastic, copal, and lac, it will appear that the latter are successively harder and more perfect as varnishes, and in proportion to their perfection as varnishes is the difficulty of using them as vehicles; and as it is necessary that before varnishing with any of them the picture should be thoroughly dry, to prevent subsequent cracking, this is perhaps more essential for the latter than for the forNotwithstanding this necessity, there is one highly important advantage which seems to attend early varnishing; namely, that of preserving the colour of the vehicle used from changing, which it is observed to do when a permanent varnish is passed over colours and tints newly laid; but this it does always at the hazard and often at the expense of cracking. This saving grace of early varnishing appears to arise from the circumstance, that, while linseed and other oils are in progress of drying, they attract oxygen, by the power of which they entirely lose their colour;

* In some trials, however, lately made upon oil-painting not firmly dried, with the white lac varnish, cracking of the varnish has not ensued.

but after becoming dry, they progressively acquire colour. It is at the mediate period between oils thus losing and acquiring colour, which commences previously to the oil becoming perfectly dry, that varnish preserves the colour of the vehicle, probably by preventing its farther drying and oxidation, which latter may in the end amount to that degree which constitutes combustion and produces colour :-indeed it is an established fact, that oils attract oxygen so powerfully as in many cases to have produced spontaneous combustions and destructive fires.

It is eminently conducive to good varnishing, in all cases, that it should be performed in fair weather, whatever varnish may be employed, and that a current of cold or damp air, which chills and blooms them, should be avoided. To escape the perplexities of varnishing, some have rejected it altogether, contenting themselves with oiling-out-a practice which, by avoiding an extreme, runs to its opposite, and subjects the work to ultimate irrecoverable dulness and obscurity.

The manufacturing processes of the varnishes now generally used have been recently detailed in the Transactions of the Society of Arts, &c., Vol. XLIX. p. 33., by Mr. J. Wilson Neil, to whom the Gold Isis Medal of the Society has been voted for the communication, as have also the processes for white lac varnish, in Vol. XLV. of the same publication.

CHAP. XXIV.

ON GROUNDS.

THE last thing in the order of our analysis is the ground and basis on which colours, pigments, and vehicles are applied in painting; and as the basis of fresco-painting is plaster, and that of water-colour painting is principally paper, the subject of grounds is chiefly of consideration with respect to painting in oil, in which mode a great variety of grounds have been employed, which have afforded a subject of wide speculation and experiment,-of many hopes and many failures, while the charm of Venetian art has been as fruitful in exciting the invention of grounds as of vehicles.

The subject of grounds belongs to our inquiry only so far as regards their influence upon colours, and needs no very elaborate consideration here. Among the various bases upon which grounds have been laid are the metals, stone, slate, plaster, woods, card, vellum, and cloths, in all their variety. The qualities requisite to a perfect basis are durability, infrangibility, and inflexibility, which neither of these substances comprise in perfection. Metals are durable and infrangible in the highest degree; but they expand and contract by the mere alterations of temperature, and are on this account subject to detach or throw off portions of the ground, and to craze the painting and varnish. Cloths, parchment, and paper bases, are infrangible and durable in a high degree, but very flexible, which is remedied in a measure by straining and stretching; they become therefore variously eligible bases. Wood comprises all the qualities of a good basis in a medial degree, and hence upon the whole panel affords the best basis. To treat of the peculiar qualities of all these in their various kinds, would carry us far beyond the bounds of utility, and the limits of our subject, to which the grounding of these is more intimate.

Grounding or priming is not in all cases necessary, as, for example, when stone, slate, glass, porcelain, &c., are employed, as was the case in some paintings of undoubted extreme antiquity; but when grounds are necessary,

as upon metal, wood, and canvas, to be eligible, such grounds must partake all the qualities of a good basis, in being neither soft, friable, nor perishable.

The early painters in oil, being also painters in fresco, and accustomed to plaster grounds, appear to have prepared their panels, &c. with plaster or stucco, upon which they employed their colours, in some cases in water, in the manner of fresco or distemper, using size to fix them, and finishing with oil vehicles and varnish; and many such pictures have stood admirably well the ordinary effects of time, as appears among the works of Paul Veronese, Titian, Correggio, and others; but, upon cloth and flexible bases, such grounds are too stiff and friable; such bases require, therefore, a ground more of their own yielding and elastic nature, and better suited to assimilate with the materials of oil-painting, such as is afforded by tempering earths and metallic oxides with the most tenacious drying-oils, and laying them evenly upon the cloths, first coated or primed with size.

The preparing of grounds on cloths, &c. is now, however, so well performed by several of our principal colourmen, and with so much improvement, as to require little comparative attention from the artist, beyond such a general knowledge of their proper qualities and effects as may enable him to choose such as are best suited to his purpose. The colour of his ground is in like manner a matter of choice, and, generally speaking, that hue is to be preferred which partakes of the ruling colour of his picture: it was probably on this account that Titian chose to paint on a red ground, when he intended to introduce much flesh in his design, or to render red principal in his picture. It is related of the same great master, who is a prime authority in all things relating to chromatic art, that, to secure the durability and cohesion of his grounds, he imbued the canvas at the back with bees'wax, dissolved in oil, a substance well calculated to resist damp in such a situation as Venice.

To preserve the elasticity of grounds, some drying oil should be introduced into the glue or size with which they are prepared; for the same purpose bees'-wax, sugar, treacle, albumen, &c., have been added with various degrees of eligibility and success. If the ground give way in any respect, the upper surface of the picture must fail also, and this is one of the principal causes of cracking, although by no means the only one. Those substances, however, which occasion cracking in the ground will occasion cracking in the painting; hence the importance of homogenity of process

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