Part 3

39. TO GIVE STEEL A TEMPER TO CUT MARBLE.--No temper can be given to steel, in which hardness is combined with tenacity, more than in that given to files, at the file manufactories, which is accomplished by the following process.--To boiling water, add about twice as much finely ground muriate of soda, as the water will dissolve, and as much rye flour as will, with the other, make a thick paste; lay a coat of this paste over the steel, (which must be ground, or filed previous to tempering,) and subject it to a full red heat, in a fire of charcoal, mixed with about a third part of animal coal, (coal of bones, horns, leather, &c.) and then suddenly plunge it three or four feet deep, in exceeding cold water. By thus immersing the steel rather deep in the water there is a double advantage; for the water which becomes heated, by contact with the steel, will rise and its place be supplied continually by fresh cold water; and at the same time, the pressure of the water on the coating of paste, will make it adhere more closely to the steel while it is cooling. The paste may then be shelled off, and the steel will be found as bright as before, or at least, will not have been essentially oxydized by the operation.

40. TO WASH IRON OR STEEL WITH COPPER.--Dissolve sulphate of copper in water, in the proportion of one to three; wash the iron or steel with it, and it will instantly be covered with reduced copper. This is best performed by applying the solution with a brush, which must be followed directly with a sponge of clear water. In this manner any letters or figures may be drawn with a camel-hair pencil, or a pen, and if it be on polished steel, the letters or flowers will assume the brilliancy of the steel and appear like highly polished copper. It may sometimes be requisite to cleanse the metal by washing it with diluted muriatic acid, that the copper may adhere the more readily. If the steel thus ornamented, be held over a charcoal fire, the copper figures become blue first; and when the steel becomes blue, the copper takes a gold colour; but is restored again to its original colour, by diluted muriatic acid.

41. TO GIVE IRON THE WHITENESS OF SILVER.--To nitric acid, diluted with an equal quantity of water, add as much mercury as the acid will dissolve; then add to the solution, three or four times as much water, and having given the iron a coat of copper, as directed in the last experiment, brush it over in the same manner with the diluted nitrate of mercury; its appearance will be equal, if not superior to that of real silver. In this manner any common, or rough iron work, may be apparently silvered at a most insignificant expense.

42. TO WASH IRON WITH TIN.--Small pieces of iron may be tinned, after being filed bright, by washing them with a saturated solution of muriate of ammonia in water and dipping them, while moist, in a vessel of melted tin. If the iron is of such form as cannot be conveniently filed, it may be immersed in nitric acid, diluted with as much water as acid; when the acid begins to act sensibly on every part, it may be washed with water, and then with the muriate of ammonia, and if a little fine rosin be sprinkled on it previous to dipping it in the tin, it may be an advantage. The iron must remain in the tin till it becomes nearly as hot as the tin, otherwise it will be coated too thick. Muriatic acid may sometimes be used, instead of muriate of ammonia, and if the iron is not filed, it will answer a better purpose. The inside of cast iron vessels may be tinned as follows: Cleanse the iron by scouring or rubbing it with a sharp grained stone, keeping the iron wet with diluted nitric acid. As the most prominent parts of the iron will be first brightened by the stone, the acid will also commence its action on the same parts, which will very much facilitate the work, while the hollows, and deeper parts of the surface, will remain untouched till the iron is nearly smooth. When this is accomplished, wash the iron with water, and then with clear muriatic acid; turn the vessel over to drain off the superfluous acid; then set it upright, and fill it with melted tin, which must be poured in cautiously, directly on the bottom of the vessel first, and the stream of tin increased till the vessel is full; then pour out the tin suddenly, and invert the vessel till it is cold. Sheets of iron are tinned, in the manufactories of tin plate, by immersing the sheets, endwise, in a pot of melted tin, the top of which is covered with about two inches depth of tallow. This tallow answers a better purpose, after it has become brown by use, than it does at first. The only preparation of the iron sheets is, to scour them perfectly clean and bright.

43. TO GIVE TIN THE WHITENESS AND BRILLIANCY OF SILVER.--To an ounce of nitric acid, diluted with an equal quantity of water, add nearly an ounce of mercury, or as much as the acid will dissolve. When this is dissolved, add to the solution, gradually, half an ounce of sulphuric acid; this will precipitate the mercury in the form of a white powder; when this has subsided, pour off the acid and add clear water; thus wash the powder from the acid, then pour off the water, and while the precipitate is moist, (or if it be suffered to dry, it may be again moistened with water,) rub it over the tin with a piece of glove leather.--Then wash the tin with water, and when it is dry, rub it pretty hard with a piece of fine woollen cloth; it will resemble polished silver.

44. TO GIVE TIN A CHANGEABLE CRYSTALLINE APPEARANCE.--Cleanse the tin by washing it with warm soap and water, and rinse it in clear water. Then heat the tin to the temperature of bare sufferance to the hand, and pour on it, or apply with a brush or sponge, a mixture of one ounce of muriatic acid, with one fourth of an ounce of sulphuric acid, and two ounces of water; then immediately wash the tin in clear water. Another method is, to apply in the same manner a solution of two ounces of muriate of soda, in four ounces of water, with one ounce of nitric acid. In either case, if the crystalline figures are not bold enough, the operation may be repeated. If a very small figure is required, the tin may be heated nearly to flowing, and plunged into cold water, slightly acidulated with nitric and muriatic acids. If a little solder is drawn over the tin with a hot iron or copper, in such manner as to form a cross, or circle, and the opposite side of the tin be afterwards crystallized, it will have a beautiful effect.

45. TO MAKE A GOLD COLOURED VARNISH FOR TIN.--To half a pint of alcohol, in a flask, add one ounce of gum-shellac, and half an ounce of turmeric, both in powder; set the flask in a warm place, frequently shaking it, for twelve hours or more; then filter or strain off the liquor, which may be occasionally diluted with new rum.--If a colour is required resembling dutch gold, a small quantity of dragon's blood may be added, or substituted in the place of turmeric.--When this varnish is used, it must be applied to the work freely and flowing, and must not be brushed or rubbed while it is drying. One or more coats of this varnish (or laquer as it is sometimes called) may be laid on the work, as the colour is required to be deeper or lighter. _Note._--To make a rose coloured varnish, proceed as above directed, only substitute one-fourth of an ounce of the best lake, finely ground, in the place of turmeric. A transparent blue varnish may also be made by means of prussian blue; and purple or green, by adding a little blue to the gold, or rose coloured varnishes. These laquers are frequently employed for washing silver bronzed ornaments, to give them the appearance of gold or copper.

46. TO MAKE SHELLAC VARNISH FOR JAPANNING.--To one quart of the best alcohol, add half a pound of the thinnest and most transparent gum-shellac; mix and shake these together, and let them stand in a warm place for two or three days; then strain the varnish through a fine flannel, and bottle it. Shellac varnish is used for japanning lamps, tea trays, &c. Any of the colours commonly used for oil painting, may be ground in this varnish and should be applied to the work with a smooth brush, and in a warm place; and the work to be japanned, should be perfectly dry and warm. _Note._--Most of the writers on the subject of japanning, have recommended seed-lac varnish; but it is a fact, though not so generally known as it ought to be, that shellac and seed-lac are the same substance; the only difference is, that shellac is in a more clarified and refined state, than that which is called seed-lac.

47. TO MAKE THE BEST COPAL VARNISH.--Take one pound of gum-copal, and melt in a flask over a brisk fire of charcoal; at the same time in another flask, boil, or heat to the point of boiling, one pint of linseed oil; as soon as the gum is melted, take it from the fire, and add the hot oil in small quantities, at the same time stirring or shaking it till they are thoroughly incorporated. Allow the mixture to cool below the boiling point of water, and then add nearly a quart of spirits of turpentine;--cork the flask slightly, and expose it for a few days to the rays of the sun, which will make it work more smooth and shining. If a larger quantity is to be made, a copper boiler, that is small at the top will answer to melt the gum in. For ordinary or coarse work, a larger proportion of oil and a little rosin may be added. If oil is used in which red lead and litharge (in the proportion of half a pound of each to a gallon of oil) have been previously boiled, the varnish will the sooner dry.

48. TO MAKE A SPIRIT VARNISH FOR PICTURES AND FANCY BOXES.--To a pint of alcohol, in a flask, add four ounces of gum-mastic, and one ounce of gum-sandarac, both in powder; expose the mixture to a gentle heat, sufficient to produce a slight ebulition for a few minutes, frequently shaking it, and the gums will be dissolved; strain the varnish through a fine flannel, bottle and cork it. Some recommend the addition of venice turpentine, by means of which, a small quantity of gum-copal, finely powdered, may also be dissolved, but as venice turpentine contains a portion of spirits of turpentine, it renders the varnish too penetrating for many purposes; and even the gum-sandarac may be omitted without any essential disadvantage. This varnish should be a little warm when used.

49. TO MAKE ELASTIC VARNISH FOR UMBRELLAS, OR HAT CASES.--To a pint of spirits of turpentine, in a flask, add one ounce of gum-elastic, cut into very small pieces; put in the cork slightly and set the flask in a warm place, where the heat may not be equal to that of boiling water, till the gum-elastic is dissolved, which may be effected in four or five hours. Then strain the solution through a strong linen or cotton cloth, and add half a pint of boiled linseed oil. _Note._--A larger proportion of gum-elastic may be dissolved, and a less quantity of oil added, by which means the varnish will be more elastic, but will not have so smooth and permanent a gloss.

50. TO VARNISH MAPS AND PICTURES.--Take a piece of linen, or cotton cambric, rather larger than the map or picture to be varnished, and draw it straight upon a frame of convenient size, and confine it at the edges by small tacks or nails. Lay a thin coat of fine rye flour paste on this, and on the back of the paper that is to be varnished; lay the paper on the cambric and press them together till the paper adheres firmly in every part. When this is dry, give the face of the print two or three coats of a strong solution of gum-arabic in water, allowing each sufficient time to become perfectly dry. This sizing must be applied with a large smooth brush, and must be spread over the work very quickly, and with as little brushing as possible. Afterwards, give the work one or more coats of the varnish described at 48. _Note._--Very small prints may not require to be pasted on cambric; and if the paper be very thick, the varnish may be applied without the previous sizing. Ising-glass, (which may be readily dissolved in boiling water) is sometimes added to the gum-arabic, and increases the strength of the sizing, but is somewhat less transparent than pure gum-arabic. A more simple method of varnishing prints, is to size them with a solution of loaf sugar, and finish with a solution of rosin in spirits of turpentine.

51. TO MAKE BRUNSWICK BLACKING FOR PICTURE GLASSES.--Take one pound of gum-asphaltum and melt it over a slow fire; then take it from the fire and add spirits of turpentine in small quantities, stirring it briskly till it is of the consistence of varnish. As there is some danger of its taking fire when the spirits of turpentine is added, it may be well to be provided with a piece of wet flannel, to throw over it if that should happen. When it is nearly cold, strain it through a flannel, and bottle it for use. This blacking is used for bordering picture glasses, and is probably the most perfect black in nature. It is water proof and dries very quick.

52. TO MAKE A PRINT APPEAR ON A GOLD GROUND.--Dilute venice turpentine with spirits of turpentine till it works freely with a camel-hair pencil; lay a coat of this varnish on any part of a print or picture, observing to keep the pencil within the lines, that the varnish may not spread beyond. Then lay a coat of the varnish on the same part of the back of the paper and lay on a leaf of gold over the varnished part; press down the gold very gently with cotton, and the varnish having rendered the paper transparent, the face of the picture will appear as if those parts were printed in gold. By this varnish (which is less liable to spread in the paper than oil) pictures may be so prepared, that the colours of various parts of them, may be varied and changed at pleasure, by placing pieces of silk or paper of different colours on the back of them.

53. BEST METHOD OF TRACING OR COPYING A PICTURE.--Perhaps the most simple method of copying the outlines of a picture, is to place the picture against a window, with the paper over it, on which the copy is to be drawn; the principal lines of the picture will be seen through the other paper, and may readily be traced with a lead pencil. But the usual manner of copying, in landscape painting, and which will answer for pictures of any size, is to rub over the back of the picture with plumbago, or red ochre; then lay the picture on the ground that is to receive the copy, and trace the lines with a smooth pointed steel, or piece of hard wood. The ground will thus be very accurately and distinctly marked, by the plumbago or ochre adhering to the ground in the lines that are traced. When several copies are to be taken from the same pattern, (which frequently occurs in ornamental painting,) the outlines of the first copy may be perforated with some pointed instrument, so that being laid on the other grounds that are to receive the copies, and brushed over with a little fine dry whiting, or red ochre, (as the case may require) the whiting or ochre will penetrate the perforated lines of the pattern, and thus mark the ground on which it is laid.

54. THE CONSTRUCTION AND USE OF A COPYING MACHINE.--Take two strips of wood, which may be about three feet long, one inch wide, and one-fourth of an inch thick; lay them on a table, parallel to each other, and eighteen inches apart. Across these, lay three other strips, which must be eighteen inches long, that each end of each piece may rest on one of the longer strips. Two of these must lie across the opposite ends of the longer pieces, and the other across the centre, thus forming two squares. Drive a pin through the ends of the short pieces, or confine them by rivets to the others, but not so as to prevent their playing circularly on the rivets. Then drive a pin or pivot through the centre of the middle cross-bar into the table, or board on which the work lies. In one end of one of the long strips (which may project a little over the cross-bar) fix a lead pencil, with the point downward, so that it may bear lightly on the board; and under this pencil, place the paper that is to receive the copy. And in the opposite end of the other piece, fix a smooth iron point, in a manner similar to that of the pencil, and under this point place the picture that is to be copied. Then with the iron point, carefully trace the lines of the picture, and the pencil in the opposite corner will move in a transverse direction, and draw the same picture very accurately on the other paper. If you fix the pencil half way between its former place and the middle cross-bar, and remove the pivot to a point that is directly in a line with the pencil and the iron point, it will give a copy in exact proportion, but only one fourth part as large as the picture that is copied. Thus the copy may be decreased or increased to any size, and still retain its regular proportions. In this manner, painting on wood or canvas may be copied, which could not readily be done in any other way.

55. TO PRODUCE THE EXACT LIKENESS OF ANY OBJECT, INSTANTLY ON PAPER.--This may be readily effected by laying the paper on a table, and holding a double convex lens (a common sun-glass) over it, and then placing a mirror over the lens, in an oblique position so as to face partly downward, and partly towards the object that is to be represented. The rays of light passing from the object to the mirror, will be reflected downward through the lens, and produce the likeness of the object in full colours on the paper. This experiment may be easily made in the evening, by reflecting the flame of a candle in this manner, which will appear very brilliant on the paper. But in order to render the reflection of an object distinctly visible by day light, it may be requisite to exclude nearly all the light from the paper, except what falls through the lens. In all cases, the lens must be placed at a distance above the paper, according to its focus, or the distance at which it would contract the rays of the sun to the smallest point. A very convenient camera obscura, for drawing landscapes, or even portraits may be constructed as follows: Make a box of boards, in the form of a regular cube, being one foot in length, breadth and height; bore a hole of one inch diameter, through the centre of the top; and on this, fix a double convex lens, the focus of which must reach the bottom of the box. Make an aperture of about six inches in length, and one in breadth, through one side of the box at the top, by shaving off, or hollowing the edge in such manner that when you put your face to the aperture to look into the box, it will exclude all the light except what falls through the lens. Make a hole through each end of the box, near the bottom, large enough to put in the hands, with paper and pencil. On the top of the box, on the right and left sides of the lens, fix two pieces of boards, which may be about four inches high, eight inches long, and three inches distant from each other. Between these boards, fix a piece of looking glass, three inches square, and facing from you; the lower edge of the glass, being near the lens, on the side towards you; and the upper edge inclining towards you about thirty degrees from a perpendicular. Directly over, and nearly four inches above the lens, place another mirror, the centre of which must face directly towards the lower edge of the first. Cover the glass-box so as to exclude all the light from the glasses except what falls on them horizontally from objects directly in front of you, and place a sheet of paper on the bottom of the box inside. The rays of light, passing from objects in front, will be reflected from the first mirror to the second, and from the second, through the lens to the paper, where you will have a perfect similitude of the objects in view, in full colours, and true perspective, and may trace them on the paper, with a pencil or pen.

56. COPPER-PLATE ENGRAVING.--For this purpose, provide a plate of copper, rather larger than the design that is to be engraved, and may be about one sixteenth of an inch thick; planish by rubbing it, first, directly length-wise, and afterwards breadth-wise with a piece of pumice-stone, which may be dipped occasionally in a mixture of one part nitric acid, with six or seven parts water.--Then wash the copper with clear water, and rub it with an oil stone that has a plane surface; and then polish it with a piece of charcoal, that has been ignited to redness and quenched in cold water. Afterwards burnish the copper by rubbing it with polished steel. Lay a piece of transparent paper on the design that is to be engraved, and trace the principal lines with a lead pencil;--then brush over the copy or tracing with dry red ochre, and having rubbed the copper plate with a piece of bees-wax, lay the red side of the tracing on the plate; then with a smooth iron point, trace the same lines again, that they may thus be transferred to the plate by means of the red ochre and wax. Take up the paper and trace the lines on the plate with a needle, thus scoring the lines slightly on the copper. Then warm the plate and wipe off the wax, or wash it off with spirits of turpentine, and rub the plate with fine dry whiting. The next instrument to proceed with is the graver; consisting of a blade of steel about three inches long, which is fixed in a convenient handle like an awl. The form of the graver should be triangular, or between a triangle and lozenge, having two sides plane and the other round or swelled; and should taper regularly from the handle to the point, or nearly so, but the point must be ground off obliquely so that the edge may extend a little farther than the back; and the edge should rise a little rounding towards the point. It is very essential that the edge and point of the graver should be kept very sharp. The manner of holding the graver, is to take the handle into the hollow of the hand, pressing it with three fingers, on one side, and the thumb on the other, and extend the fore finger on the back of the blade towards the point.--The edge of the graver must rest on the plate, and its motion when cutting must be endwise in all cases; though there evidently might be a graver constructed, which might, in some cases, be handled in a manner more similar to that of a pen or pencil. A graver of a square form may also be requisite, for cutting large and broad lines occasionally. In proceeding to engrave the plate, begin with the outlines, observing to press harder or lighter on the graver, as the lines require to be larger or smaller, and finish each line with the same motion if possible, without taking the graver off the plate. Having cut the outlines, proceed to fill up, and shade the work discretionally, according to the design. It may be requisite, after part of the work is engraved, to scrape it lightly with the edge of the graver, to take off any roughness, that may have been formed on the part engraved. If after finishing the design, any part appears to have been improperly executed, such parts may be erased by the burnisher, and may be re-engraved with the requisite amendments.