ness.

Ornamented work must be polished with the same materials as plain work, using brushes instead of linen, and ruboing as little as possible; otherwise, the more prominent parts will be injured. The polishing material should be washed off with clean water, and when dry may be rubbed with a clean brush.

Horn and tortoiseshell are so similar in their nature and texture that they may be classed together, as regards the general mode of working and polishing them. A very perfect surface is given by scraping; the scraper may be made of a razorblade, the edge of which should be rubbed upon an oil-stone, holding the blade nearly upright, so as to form an edge like that of a currier's knife, and which, like it, may be sharpened by burnishing. Work, when properly scraped, is prepared for polishing. To effect this, it is first to be rubbed with a buff, made of woollen cloth, perfectly free from grease; the cloth may be fixed upon a stick, to be used by hand; but what the workmen call a bob, which is a wheel running in the lathe, and covered with the cloth, is much to be preferred, on account of the rapidity of the operation. The buff is to be covered either with powdered charcoal and water, or fine brick-dust and water; after the work has been made as smooth as possible with this, it is followed by another buff, or bob, on which washed chalk, or dry whiting, is rubbed; the comb or other article to be polished

Pigments. INDIAN RED.-When pure this is a native mineral production, it is manufactured artificially by calcining sulphate of iron until the water of crystallization is expelled, then roast it with a fierce fire until acid vapours cease to arise; cool, wash the remainder with water until the water ceases to affect litmus paper, then dry. An inferior quality is made by calcining 11 parts common salt with 25 parts green sulphate of iron, wash well with water, dry, and powder the remainder. As thus prepared Indian red is the same as jewellers' rouge and colcothar. When used as a pigment it is frequently mixed with red ochre. It is a very permanent colour, can be made of different tints, and is especially useful in fresco and silicious painting. The finest Indian red or crocus usually undergoes a second calcination, in which it is exposed to a very intense heat.

LIGHT RED, made from yellow ochre by careful calcination. This colour mixes well with both oil and water, and gives a capital flesh colour when mixed with white.

RED CHALK.-A natural clay containing nearly protoxide and carbonate of iron.

RED-LEAD. Prepared by placing ground and well-washed massicot in iron trays piled up on the hearth of a reverberatory furnace, in a heat of from 600° to 650° Fahr., stirring it occasionally until of the proper colour.

Massicot (Protoxide of Lead).-Genuine massicot is the strongest oxide of lead, and its colour is a dull orange yellow, but artists occasionally apply the term massicot to white-lead roasted until it turns yellow. In the preparation of minium the lead is calcined in a reverberatory furnace; this process gives a mixture of massicot and lead; these are separated by washing and trituration; the massicot being much lighter remains

suspended in the water; it is drawn off, and left to settle; the deposit which it then forms is collected and dried, and this is the true massicot. It may be employed with advantage in preparing the drying oils; it produces the same effect as litharge when very finely ground. It may be employed as a colour; its tint is not brilliant; but as it is a better drier than white-lead, it may be substituted for it in mixing with colours which dry with difficulty, as the lakes and the bituminous earths.

Minium.-A higher degree of oxidation transforms the massicot into minium. On a large scale minium is prepared by calcining massicot in reverberatory furnaces; it becomes first of a dark orange colour, then purple, but this last tint disappears on its cooling; when at this point, the doors of the furnaces are closed, but not hermetically, so as to allow of a little air entering. The massicot cools very slowly; and as it absorbs the oxygen of the air, it becomes of a strong orange colour and grows finer in proportion to the slowness of its cooling. If instead of massicot we calcine ceruse, a peculiar red, called "mineral orange," is obtained; it is a minium, but of a tint more pure and brilliant than any of its class.

TO TEST RED-LEAD.-There are few substances to be found which can be mixed with red-lead without injuring its brilliant colour. Nevertheless, it is often mixed with brick-dust or red ochre. For detecting brick-dust, heat the red-lead in an earthen crucible, and then dissolve it in diluted nitric acid. If brick-dust is present it remains undissolved. To detect red ochre, boil the red-lead in muriatic acid; dilute the solution with water and filter it. Add to a portion of the clear solution a solution of yellow prussiate of potash, and to another portion an excess of a solution of caustic potash. If the first reagent produces a dark blue precipitate, and the second a brown precipitate, the red-lead contains red ochre. VERMILION. - Vermilion is a sulphide of mercury; it may be used in oil, water, fresco, and silicious painting. In all cases, however, it gets slightly darker

in time; this is not a chemical but a physical change. With the exception mentioned, this pigment is very permanent. Vermilion is composed of mercury and sulphur, very intimately combined. It is found naturally formed in the quicksilver mines; but that which is used in painting is an artificial production. 1. Vermilion is prepared by melting one part of sulphur, and adding to it gradually five or six parts of mercury; the heat is continued until the mixture swells up, then cover the vessel and remove it from the heat; when the mixture is cold reduce it to powder and sublime in a closed vessel so placed in a furnace that the flames may play freely around it to about half its height. The heat is gradually increased until the lower portion of the subliming vessel becomes red hot; the cold sublimate is broken into pieces, ground in water to a fine powder, passed through a sieve and dried.

At first the mixture becomes black, takes the name of Ethiops mineral, or black sulphuret of mercury; this substance is then reduced to powder, and sublimed in appropriate vessels, when a crystallized mass is obtained, composed of bright filaments of a violet tint; by trituration it becomes of a scarlet colour. But the mere grinding will not be sufficient to give a bright tone to the vermilion ; various methods are employed for that purpose, which are not generally known. Some manufacturers grind these ingredients up with plain water or with urine, and afterwards boil it for some time; others treat it with nitric acid; but it does not happen that any of the methods hitherto employed for heightening the colour of vermilion obtained by sublimation, give the same brightness as the Chinese vermilion, the preparation of which is not known. 2. Quicksilver 300 parts, flowers of sulphur 114 parts, grind them together or some hours and then add gradually 75 parts caustic potash dissolved in 450 parts water; continue the grinding for some time longer, then gently heat the mixture in an iron vessel, first stirring constantly, but afterwards only at intervals, keeping the heat as near 115° Fahr as

possible, and observing to add fresh water as the evaporation takes place. When the colour begins to redden great care is necessary to preserve the mixture at the proper temperature and to keep the sulphuret of mercury quite pulverulent. As soon as the colour is nearly fine the process must be conducted with increased caution and at a lower heat for some hours, until a rich colour is produced. This is well washed in water and dried. It is very injurious for those employed to inhale mercurial vapours, for which reason this operation should be performed only in a place where the chimney has a good current of air; there also should be fixed to the tube of glass with which the mixture is stirred a staff sufficiently long to hold at good distance from the vessel; in the same way the spoon should be lengthened with which the potash is added.

CARMINE. Boil 1 lb. of cochineal and 4 drs. carbonate of potassa in 7 galls. of water for quarter of an hour. The pot is taken from the fire and 8 drs. alum in powder mixed into the liquor, which is afterwards well stirred and then allowed to settle for 20 minutes or so. The liquid is poured into a fresh vessel and a solution of 4 drs. fish glue or isinglass, dissolved in a pint of water and strained, mixed with it. When a skin is formed upon the surface the heat is taken away and the liquor rapidly stirred, and allowed afterwards to settle for half an hour or so, when the deposited carmine is carefully collected, drained, and dried.

PAINTERS' CREAM.-Pale nut-oil, 6 oz., mastic 1 oz.; dissolve; add oz. of sugar of lead ground in a little oil; then add water, gradually, until it acquires the consistence of cream, working it well all the time. Used by painters to cover their work when they are obliged to leave it for some time. It may be washed off with a sponge and water.

Lakes.-Lakes are made by adding a solution of alum, either alone or partly saturated with carbonate of potassa, to a filtered infusion or decoction of the colouring substance, and after agitation precipitating the mixture with a solution of carbonate of potash; by precipitating

a decoction or infusion of the colouring substance made with a weak alkaline lye, by adding a solution of alum; or by agitating recently-precipitated alumina with a solution of the colouring matter, prepared as before, until the liquid is nearly decoloured, or the alumina acquires a sufficiently dark tint. The first method is usually employed for acidulous solutions of colouring matter, or for those whose tint is injured by alkalies; the second, for those that are brightened, or at least uninjured by alkalies; the third, for those colouring matters that have a great affinity for gelatinous alumina, and readily combine with it by mere agitation. By attention to these general rules, lakes may be prepared from almost all animal and vegetable colouring substances that yield their colour to water, many of which will be found to possess great beauty and permanence. The precise process adapted to each particular substance may be easily ascertained by taking a few drops of its infusion or decoction, and observing the effects of alkalies and acids on the colour. The quantity of alum or of alumina employed should be nearly sufficient to decolour the dye liquor, and the quantity of carbonate of potassa should be so proportioned to the alum as to exactly precipitate the alumina without leaving free or carbonated alkali in the liquid. The first portion of the precipitate has the deepest colour, and the shade gradually becomes paler as the operation proceeds. A beautiful tone of violet, red, and even purple may be communicated to the colouring matter of cochincal by the addition of perchloride of tin; the addition of arseniate of potassa in like manner gives shades which may be sought for in vain with alum or alumina. After the lake is precipitated, it must be carefully collected, washed with cold distilled water, or the purest rain water, until it ceases to give out colour, and then carefully dried in the shade. In this state it forms a soft velvety powder.

DROP LAKE is made by dropping the moist lake through a small funnel on a clean board or slab, and drying it by a gentle heat. A very little clear gumwater is commonly added to the pasto

to give the drops consistence when dry. Synonymous with Brazil-wood Lake.

BLUE LAKE.-A fugitive colour prepared from some of the blue-coloured flowers. The name is also applied to lump archil, to moist alumina coloured with indigo, and to mixed solution of pearlash and prussiate of potash, precipitated with another solution of sulphate of iron and alum. These are permanent and beautiful, but are seldom used, in consequence of indigo and Prussian blue supplying all that is wanted in this class of colours.

BRAZIL-WOOD LAKE.-1. Ground Brazil-wood, 1 lb.; water, 4 galls.; digest for 24 hours, then boil for half an hour, add alum, 1 lb., dissolved in a little water; mix, decant, strain, and add a solution of tin, lb.; again mix well and filter; to the clear liquid add, cautiously, a solution of salt of tartar or carbonate of soda, as long as a deep-coloured precipitate forms, carefully avoiding excess; collect, wash, and dry. The product is deep red. By collecting the precipitate in separate portions, lakes varying in richness and depth of colour may be obtained. The first portion of the precipitated lake has the brightest colour. An excess of alkali turns it violet, and the addition of cream of tartar, brownish red. The tint turns more on the violet red when the solution of tin is omitted. Some persons use less, others more, alum. 2. Add washed and recently-precipitated alumina to a strong and filtered decoction of Brazil-wood. Inferior to the last.

CARMINATED LAKE.-1. The residuum of the cochineal left in making carmine is boiled with repeated portions of water, until it is exhausted of colour; the resulting liquor is mixed with that decanted off the carmine, and at once filtered; some recently-precipitated alumina is then added, and the whole gently heated, and well agitated for a short time; as soon as the alumina has absorbed sufficient colour, the mixture is allowed to settle, after which the clear portion is decanted, the lake collected on a filter, washed, and dried. The decanted liquor if still coloured is now treated with fresh alumina until exhausted, and

| thus a lake of a second quality is obtained. 2. To the coloured liquor obtained from the carmine and cochineal as above, a solution of alum is added, the filtered liquor precipitated with a solution of carbonate of potassa, and the lake collected and treated as before. Scarcely so good as the last. Some makers mix a solution of tin with the coloured liquor, adding the alum or alumina; this brightens the colour. The above lake is a good glazing colour with oil, but has little body.

COCHINEAL LAKE.-1. 1 oz. cochineal in coarse powder; water and rectified spirit, of each, 2 oz.; digest for a week, filter, and precipitate the tincture with a few drops of solution of tin, added every 2 hours, until the whole of the colouring matter is thrown down; lastly, wash the precipitate in distilled water, and dry it. 2. Digest powdered cochineal in ammonia water for a week, dilute the solution with a little water, and add the liquid to a solution of alum, as long as a precipitate falls, which is the lake. 3. Coarsely - powdered cochineal, 1 lb., water, 2 galls.; boil 1 hour, decant, strain, add a solution of salt of tartar, 1 lb., and precipitate with a solution of alum. By adding the alum first, and precipitating the lake with the alkali, the colour will be slightly varied. All the above are sold as Carminated or Florence Lake, to which they are often superior.

GREEN LAKE.-Made by mixing blue and yellow lake together. Generally prepared extemporaneously by the artist on his palette.

LAC LAKE.-Boil fresh stick-lac in a solution of carbonate of soda, filter the solution, precipitate with a solution of alum, and proceed as before. A fine red.

MADDER LAKE.-1. Crop madder, 2 oz.; tie it in a cloth, beat it well in a pint of water in a stone mortar, and repeat the process with about 5 pints of fresh water until it ceases to yield colour; boil the mixed liquor in an earthen vessel, pour it into a large basin, and add 1 oz. of alum, previously dissolved in a pint of boiling water; stir well, and while stirring, pour in gradually of a