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(From The Household Cyclopedia, 1881)
The different modes of engraving are the following:
- In strokes cut through a thin wax, laid upon the plate, with a point, and these strokes bitten or corroded into the plate with acid. This is called etching.
- In strokes with the graver alone, unassisted by acid. In this instance, the design is traced with a sharp tool, called a dry point, upon the plate, and the strokes are cut or ploughed upon the copper with an instrument distinguished by the name of a graver.
- In mezzotinto, which is performed by a dark ground raised uniformly upon the plate with a toothed tool.
- In aquatinta, the outline is first etched, and afterwards a sort of wash is laid by the acid upon the plate, resembling drawings in Indian ink, bistre, etc.
- On wood.
Etching is a method of working on copper or steel, wherein the lines or strokes, instead of being cut with a graver, are eaten with acid.
The principal materials for this art are, the copper or steel-plate, hard and soft ground (the first for winter, and the other for summer), a dabber, turpentine-varnish, lampblack, soft wax, and aqua-fortis.
The tools are an oil-rubber, a burnisher, a scraper, a handvice, etching-boards, etching-needles, an oil stone, and a parallel ruler.
So called because the result is produced by a combination of lines of various sizes, forms, lengths and textures, is the most beautiful and useful style of multiplying copies of works of art. All other modes are only efforts at lessening cost, not of excelling in quality. In producing a plate upon this principle, cutting with the graver, etching with the point, and biting or corroding with acids, are the ordinary means employed. This combination of chemical and mechanical together with the artistic, is universal in line engraving. Gravers are of various shapes; those most useful, however, are the lozenge and square. With lines laid in and cut up with this tool, it is useful to represent drapery, hair, flesh, in fact all that pertains to human figure, while with lines slightly cut into the metal through an etching ground bitten with acid and finished with the assistance of the graver, that kind of line and character of manipulation best calculated to represent landscape, architecture, animals, etc., is obtained, as the steel point with which the etching is done is used much in the manner of a pen or leadpencil, an ease, freedom and disposition of line is secured, which cannot result from the use of the graver alone. The burnisher is also an important tool, as by a skilled use of this instrument much of the delicacy and tenderness which characterizes a well finished line engraving, is obtained. The scraper is principally used to free the lines made by the other tools from the burr, or roughness which accompanies their application. It is intended in this article to treat of engraving on steel. Copper is now seldom used, but the remarks and instructions, axcept in so far as biting is concerned, are equally applicable to both. Nitrous acid diluted with water is the medium of corroding copper; nitric diluted with acetic, or even with water, is used for steel. The plates, properly prepared, can be obtained of the manufacturers.
Is composed of burgundy pitch, 3 parts; asphaltum, 3 parts; beeswax, 1 1/2 parts. Increase the wax in proportion to the desired softness; when thoroughly melted by heat, pour into hot water, and work into balls of convenient size.
Take a ball of etching ground, break it into pieces of convenient size, place them in a bottle, and pour on sulphuric ether. If too thick, add ether; if too thin, take the cork out until it evaporates to proper consistency.
To Lay a Solid Ground.
Put a ball of ground into a piece of silk, make a dubber with a circular piece of pasteboard from 2 to 3 in. in diameter, and a pad of wadding on one surface about 1 inch in thickness, tied in a piece of kid-skin or good smooth silk, disposed evenly over this on the under side. Clean the surface of the plate thoroughly with whiting or air-slaked lime; attach in hand-vice; heat the plate until hot enough to boil spittle on the back; rub the ground evenly over the surface required, and use the dabber to distribute it smoothly. If the plate has cooled, heat again to former temperature, then turning the ground downwards, with a lighted candle or taper moved slowly back and forth, as near the surface as may be without touching the ground with the wick, smoke it till sufficiently black. Carefully avoid dust during the whole operation.
To lay Liquid Ground.
Clean the surface of the plate, first with turpentine, then a clean rag and whiting; take an ordinary etching dabber, or make a small ball with raw cotton, cover it with a piece of silk velvet, carefully drawn tight to avoid creases, then dip the dubber in the liquid or pour it on the plate and draw and streak it quickly and evenly; the evaporation of the ether leaves a clear, firm ground.
To Transfer the Outline to the Surface.
Various plans are used. If the design to be copied be the size to engrave, the outline may be traced with a pencil on a piece of oil-paper laid over it. This tracing may be transferred by laying it upon the ground, and while damp passing it through the printing press with a piece of damp printing paper laid over it. It may also be retraced upon the ground by laying between the tracing and plate a piece of thin paper, coated on the under side with vermilion or blacklead, and going carefully over the outline with a blunt point, or lead-pencil.
A better plan is to use gelatine paper. Trace the outline on this article with a sharp point, cutting into it; scrape off the raised edges from the lines with a smooth scraper; then fill the cuts with vermilion or black-lead; carefully wipe off the superfluous dust; lay in proper position, fix down with wax, and, while slightly damp, pass it through the printing press, or with the gelatine dry burnish over the back sufficiently firm to set off the outline, taking care not to break the ground. The best and most recent mode is to get a daguerreotype of the design, the requisite size; cut cleanly and smoothly with a sharp point into the copper over all the outline; this done, remove all the raised edges with the scraper, and get an impression from the copper. While this is still damp place it on the ground and pass it through the press. If the impression has been taken with red ink, the outline will at once appear; if in black, pass a hair-pencil dipped in vermilion lightly over the ground, which must be first freed from damp, so that the vermilion may adhere only to the oil from the impression.
Fix down with wax, strips of wood or leather about 1/8 in. thick upon the margin. The best and most useful point, is a good stub small round file. Set it true in a tube, such as are used for handles for parasols; grind off the cutting, and smooth on an oilstone. The point must be sharpened by rolling it between the palms of the hands, keeping the point on the stone; when once set, it can be easily put in order, by holding it in the right hand, and, while causing it to rotate between the thumb and second finger, draw it smoothly down upon a piece of fine emery paper until the point is perfectly round and sharp, extreme sharpness being undesirable. Hold the point nearly perpendicular between the finger and thumb, draw it without pressure, gently over the emery. The examination of a good specimen of the art will give the best idea of the necessary width, style, etc. As a general rule, the more distant parts are etched close, and the space between the lines should increase, as the approach is made forward. Sufficient pressure must be exerted to cut well into the steel, yet not enough to impede an easy motion. Cut with a steady and equal pressure, so that the lines may all present the same color to the eye, as all inequalities show when bitten.
Biting Hard Steel.
The etching completed, carefully cover the un-etched surface of the plate with stopping-out varnish, composed of asphaltum dissolved in turpentine, or gum resins, or good sealing-wax, dissolved in alcohol. When dry, form a well around the work, of walling wax, composed of beeswax and burgundy pitch, equal parts dissolved together. Make a convenient spout by which to pour off the acid. The best acid for biting the steel in ordinary use is the commercial nitric, 1 part; acetic, 3 parts. For delicate tints, such as skies, distances etc., this mixture may be diluted at pleasure with water to any extent, down to the sharpness of strong vinegar. Steel is acted upon by acid, with great rapidity as compared with copper; it must therefore be quickly put on, and quickly removed, and luke-warm water poured over the surface; blow dry with the bellows; the operation is much facilitated by heating both the plate and acid.
Scrape off small portions of the ground on the lighter parts, to judge thereby of the quality of line, and stop out carefully all that may be considered dark enough. Continue this process until the stronger portions assume sufficient color for the first biting.
Biting Soft Steel.
The use of acids even on hard steel is uncertain and precarious, much more so on soft or partially decarbonized; on such nitric acid being unsatisfactory, resort is had to other materials in search of that success denied to the ordinary means.
1. Corrosive sublimate, 1/4 oz.; alum, 1/4 oz.; dissolved in a pint of warm water, bites a fair line. Keep sweeping off the sediment deposited during the process, with a hair-pencil or feather.
2. Spencer’s, or magnetic acid; dissolve in 1/2 oz. of commercial nitric acid and the same quantity of water, and 1 oz. of fine silver. In the like proportions, of acid and water, dissolve 1 oz. of mercury. Then mix solution of silver and of mercury, each, 1 part; water, 25 parts; solution of nitric acid, 1/2 part.
This mixture bites very rapidly when once started; it will, however, lie perfectly inactive until some one of the following plans is used. 1. Heat a steel point by rapid friction or fire, and with it touch the steel through the acid and ground; a black deposit at once forms; sweep it off with a feather. 2. With a strip of zinc polished at both ends, touch with one end the acid, and with the other, a clear piece of steel. 3. Wet a part of the surface of the plate with spittle; this is a very ready means. 4. Dip a point in corrosive sublimate; this pressed into the steel will force action; or, 5. Put corrosive sublimate on for a moment, pour rapidly off, and as quickly put on the magnetic acid.
To Set and Use the Graver.
Lay the sides, the angles of which form the belly, on the oil-stone; rub gently, taking care to keep the part flat upon the stone, until the edge is sufficiently sharp; then, with the handle of the graver in the hollow of the hand, and the forefinger on the belly, hold it at an angle of about 30 degrees, and rub the end till a good point is obtained. In cutting, hold the handle of the graver in the hollow of the hand, and the graver between the forefinger and thumb, the plate lying solid upon the table, turning it as occasion may require. The outlines of figures are usually dotted in with the etching, slightly bitten, and stopped out, and the serious part of figure engraving now commences, by laying in the lines, according to the taste and skill of the workman, lightly at first, and gradually cutting deeper and broader into the darker parts. Sand-bags and oil-rubbers are exploded institutions.
Etch the outline, bite slightly in the distance and light parts; more strongly those near at home. Clean the plate well to lay the ground, which is thus done: dissolve resin in proof alcohol; for distance, less resin is required. Increase the quantity for the nearest parts. Pour this mixture over the plate, run off the superfluous matter, and in drying it will form a granulation on the surface. This granulation is fine or coarse in proportion to the quantity, more or less, of resin contained in the alcohol. When the resin is in excess no granulation will form. Stop out, bite, and re-bite, as in etching.
So called from the circumstance that the subjects treated by this method in the earliest period after its invention, were such as admitted of a large amount of middletint or half-tone in the distribution of the masses of light and dark, it being then believed that such only were suited to this style of art. The process is of the utmost simplicity, and as the best general idea of it may be obtained from the anecdote related of what suggested the invention, it is perhaps advisable to begin by repeating the story, whether founded on fact or not.
Prince Rupert, to whom its origin is popularly attributed, is said to have taken the idea from observing a soldier in camp polishing a rusty sword. The rust had been, on some parts of the blade, entirely removed, while on others it remained in all its original roughness, and in some portions the polishing was half done. This accident suggested that a rapid and effective style of engraving might result, if a metal plate were roughened all over its surface by some means, so that it would take secure hold of a coating of plate-primers’ ink when applied, and then, being again removed by grinding, or scraping, or burnishing wherever the middle tints and lights of the picture required, would thus retain the printers ink just in proportion to the degree of such removal. Where the plate was polished bright, the ink would readily wipe clean away, and in printing leave the paper unstained, forming the high lights of the picture, while in the parts where the roughening was left the ink would refuse to wipe away, and thus would print the extreme darks of the picture. Such was the theory framed; the result of experiment proved it to have been well founded, and mezzotinto, a compound Italian term, signifying middle-tint, took a permanent and respected position among the arts. So it is already seen that the operation of mezzotinto engraving is exactly the reverse of every other kind, being from dark to light; as in drawing a picture by means of white chalk on black paper, or by taking a panel of lightcolored wood and having charred with fire the whole surface to blackness, scrape this away again in various degrees of completeness in such manner as to present the lights and shadows of a picture.
The contrivance first used for producing the roughened surface on the copper-plate, termed the mezzotinto ground, was a wooden roller, in which were securely fixed multitudes of steel points, sharp ends outwards. This was rolled over the plate with moderate pressure, backwards and forwards in every direction, until no particle of the original polished surface remained unpunctured by a dot. But the difficulty presented itself of there being no means of sharpening the steel points when they broke off, or were worn dull by repeated use. Consequently there was substituted, in place of the roller, the instrument called the rocker, or cradle-tool, or more properly the grounding tool, which continues in use to the present day, notwithstanding its obvious imperfections, for it can easily be sharpened when dull, lasts a long time, and nothing better has yet been thought of. The grounding tool is made in from like a broad chisel, two inches wide, cut all over one side with grooved straight lines parallel to each other, exactly equi-distant and of equal depth. These run lengthwise on the tool, so that when the end is sharpened to a bevel, they form a saw-like edge of teeth. The toothed edge being sharpened to a curved shape, the tool is held in a nearly upright position, its teeth resting on the plate, and is rocked from side to side, advancing forward with a slightly zigzag motion. The handle, attached to a shank at the upper end, is firmly grasped, the wrist being kept stiff. The elbow rests on the table as a pivot of the motion. Guide-lines are drawn on the plate with a pencil or charcoal against a ruler, parallel to each other, and not quite so wide apart as the breadth of the tool. The grounding tool is then held in the position described, not quite upright, but slightly inclined forwards, the middle of the tool midway between the lines, and the elbow in place so that an imaginary line between it and the tool is in the same direction as the pencil guide-lines on the plate. The rocking motion is then made with moderate pressure, stopping on each side as nearly on the guide-line as possible, great care being observed to avoid digging in the corner of the tool by rocking too wide a line, and also to avoid rocking repeatedly in the same place, thus making a deep irremediable cut. Having continued this operation until all the spaces between the lines have been rocked through, what is termed one way has been completed. Precisely the same operation is repeated with the guide-lines in another direction, and then in another, and so on until a full black ground has been produced, which is when every particle of the original polish has disappeared. It is well to make a scale to assist in varying the direction of the ways, such as a half circle of paper with lines drawn on it radiating to the circumference, like the spokes of a wheel; the straight edge of the paper being laid against the edge of the plate, the ruler is laid against one of the lines as a guide for the direction about to be worked.
The outline of the intended picture is then made on the ground, either by sketching it delicately with the end of the burnisher, using it as a pencil, aided by division squares; or by transferring an outline previously drawn upon paper, on to the plate by means of the copperplate roller press. The entire effect is next obtained by scraping away the ground to various degrees of lightness, scraping it entirely away only where the highest lights of the picture are, and leaving it totally unscraped only where the extreme darks are. All the sudden bright lights of the picture are made with the burnisher, and also the pure white lights are finished with it. The scraper used is a simple band of steel, about 3/8 of an inch wide, and not quite thin enough to spring or bend. In using, sharpened lancet-like towards the end where it is applied to the plate, both edges being used. It is, when new, 4 or 5 inches long, and is employed without a handle. A correct judgment of the progress of the work can only be had by occasionally procuring a proof of the plate from the printer, during the progress.
As the plate almost always yields an impression darker than would be expected, the engraver is not apt to scrape his tints too light, but if this should happen, the tint must be replaced by means of the grounding tool. To do this it is only necessary to lay what is termed a gauze ground over the part requiring renewal; that is, a ground composed of but from five to seven crossings, seldom more.
Then scrape away again delicately to the proper degree of lightness. If a light form should have been inadvertently extended too far over on to its adjoining tint, the defect may be corrected by puncturing a few rows of dots by means of the rulette, a tool resembling a horseman’s spur, only on a minute scale, and then delicately removing the burr raised with a very sharp scraper.
The foregoing description is of mezzotinto pure and simple, but it has become the practice of late years to aid and support it largely by a foundation of etching, in lines and dots. This is all done on the plate before commencing the mezzotinto ground. The process is described under its proper head. The drawing of the outline on the plate with the burnisher is then rendered unnecessary, as the etched forms are faintly visible through the ground. The field of application of this style of engraving has been immensely widened since the introduction to the engravers’ use of plates of annealed or softened steel, which occurred about the year 1820, or a little earlier.
Previous to that, copper had been the metal in use from the time of Tomaso Finiguerra, the Florentine goldsmith, who, in 1460, invented the important art of plateprinting. Mezzotinto engraving was invented in the earlier part of the seventeenth century, most probably by Ludwig von Siegen, an officer in the service of the Landgrave of Hesse. There is a portrait print by him in this style extant, of Amelia Elizabetha, Princess of Hesse, dated 1643.
To Engrave On Wood.
The block is commonly made of pear-tree or box, and differs in thickness according to its size. The surface for the engraving is on the transverse section of the wood; the subject is drawn upon it with a pen and Indian-ink, with all the finishing that is required to have in the impression. The spaces between the lines are cut away with knives, chisels, and gouges, leaving the lines that have been drawn with the ink.
The taking impressions from blocks of wood differs from that of copper-plate in this, that in the latter they are delivered from the incision, while in the wooden blocks they are delivered from the raised part.
To Prepare Box-wood for Engraving.
The wood being chosen, and cut into a proper form and size, it must be planed as evenly and truly as possible, andwill be then ready to receive the drawing or chalking of the design to be engraved.
Now take white-lead and temper it with water, by grinding; then spread it first thinly on the surface by a brush pencil, and afterwards rub it well with a fine linen rag, while yet wet, and when it is dry, brush off any loose or powdery part by a soft pencil.
If the design be sketched on the wood by drawing, it may be done by Indian or common ink (but the first is far preferable), either by a pen or pencil, or by a black-lead pencil, though that scarcely marks strongly enough for finer work.
This method of engraving is performed with three blocks. The outline is cut in one, the deep shadows in a second, and the third gives a tint over the whole, except where the lights are out away. These are substituted in their turn, each print receiving an impression from each block. This mode of engraving was designed to represent the drawings of the old masters.
To Secure Copper-plates from Corrosion.
Take equal parts of wax and turpentine and double the quantity of olive oil, with the same quantity of hog’s lard. Melt the whole over the fire in an earthen vessel, taking care to mix the ingredients well, and leave them to boil some time, till they are well incorporated.
The advantage of this mixture is: that it may at any time, being warmed, be put with the finger on the places desired to be covered; by which means the further operation of the aqua-fortis on such places may be instantly prevented without any other trouble or preparation, or without interrupting or delaying the principal operation. This mixture may be employed equally well with the hard as with the soft varnish. The intention of using such a composition is, if any scratches or false strokes happen in the etching they are to be stopped out with a hair-pencil dipped in this composition, mixed with lampblack, previously to laying on the aqua-fortis, or, as it is called, biting in.
To Choose Copper for Engraving.
Plates intended for engraving ought to be of the best copper, which should be very malleable, firm, and with some degree of hardness, free from veins or specks. The redness of copper is a presumptive mark of its being good, but not an infallible one; for though it is, in general, a proof of the purity of the copper, yet it does not evince that the qualities may not have been injured by too frequent fusion.
Copper-plates may be had ready prepared in most large towns, but, when these cannot be had, procure a pretty thick sheet of copper, rather larger than the drawing, and let the brazier planish it well; then take a piece of pumice-stone, and with water rub it all one way, till it becomes tolerably smooth and level. A piece of charcoal is next used with water for polishing it still farther, and removing the deep scratches made by the pumice-stone, and it is then finishod with a piece of charcoal of a finer grain, with a little oil.
To Etch upon Glass.
Procure several thick, clear pieces of crown-glass, and immerse them in melted wax, so that each may receive a complete coating, or pour over them a solution of wax in benzine. When perfectly cold draw on them, with a fine steel point, flowers, trees, houses, portraits, etc. Whatever parts of the drawing are intended to be corroded with the acid should be perfectly free from the least particle of wax. When all these drawings are finished the pieces of glass must be immersed one by one in a square leaden box or receiver where they are to be submitted to the action of hydrofluoric acid gas, made by acting on powdered fluor-spar by concentrated sulphuric acid. When the glasses are sufficiently corroded they are to be taken out, and the wax is to be removed by first dipping them in warm and then in hot water, or by washing with turpentine or benzine. Various colors may be applied to the corroded parts of the glass, whereby a very fine painting may be executed. In the same manner sentences and initials of names may be etched on wineglasses, tumblers, etc.
Glass may also be etched by immersing it in liquid hydrofluoric acid, after having been coated with wax and drawn on, as in the last method. There is this difference, however, in the use of the liquid and the gas, that the former renders the etching transparent, whilst that produced by the gas is quite opaque.
In this method the potassa of the glass is set free, whilst the silex or sand is acted on, consequently no vessel of glass can ever be employed with safety to contain this acid in a liquid state, as it would soon be corroded into holes. It is, therefore, generally preserved in leaden bottles, on which it has no power to act.
Glass in Imitation of Muslin.
This is a simple and ingenious means of giving to glass the appearance of delicately-wrought muslin. The process, which comes to us from Germany, consists in spreading very smoothly a piece of lace or tulle and covering it with some fatty substance by means of a printer’s roller. The glass being carefully cleaned, the cloth is laid upon it so as to leave in fat a print on the surface of all the threads of the fabric. The glass is then exposed about 5 minutes to the vapors of hydrofluoric acid, which roughens the spaces between the lines and leaves the polish on the surface under the fat.
A glass thus prepared becomes like a veil, protecting from exterior indiscretion persons who from their apartment, desire to look commodiously outside.
To Transfer Engravings to Glass.
Fix the printed surface to the glass with ordinary paste. Etch with liquid hydrofluoric acid s. g. 1.14. At the end of 3 or 4 minutes wash off the paper, and the design will be found reproduced upon the glass, the printers’ ink having protected it. Mr. Napier, the patentee, prefers to have the glass ground enamelled or veneered beforehand, when the object stands out in relief. If the veneer or enamel is colored, of course the picture remains colored, while the body of the glass is white.
To Engrave on Precious Stones.
The first thing to be done in this branch of engraving is to cement two rough diamonds to the ends of two sticks large enough to hold them steady in the hand, and to rub or grind them against each other, till they be brought to the form desired. The dust or powder that is rubbed off serves afterwards to polish them, which is performed by a kind of mill that turns a wheel of soft iron. The diamond is fixed in a brass dish and, thus applied to the wheel, is covered with diamond dust, mixed up with oil of olives; and when the diamond is to be cut facet-wise, first one face and then another is applied to the wheel. Rubies, sapphires, and topazes are cut and formed the same way on a copper wheel, and polished with tripoli diluted in water. Agates, amethysts, emeralds, hyacinths, granites, rubies, and others of the softer stones, are cut on a leaden wheel moistened with emery and water, and polished with tripoli on a pewter wheel. Lapis-lazuli, opal, etc. are polished on a wooden wheel. To fashion and engrave vases of agate, crystal, lapislazuli, or the like, a kind of lathe is made use of, similar to that used by pewterers, to hold the vessels, which are to be wrought with proper tools. The engraver’s lathe generally holds the tools, which are turned by a wheel, and the vessel cut and engraved, either in relievo or otherwise, the tools being moistened from time to time with diamond dust and oil, or at least emery and water. To engrave figures or devices on any of these stones, when polished, such as medals, seals, etc., a little iron wheel is used, the ends of whose axis are received within two pieces of iron, placed upright, as in the turner’s lathe, and to be brought closer, or set further apart, at pleasure; at one end of the axis are fixed the proper tools, being kept tight by a screw. Lastly, the wheel is turned by the foot, and the stone applied by the hand to the tool, then shifted and conducted as occasion requires.
The tools are generally of iron, and sometimes of brass. Their form is various: some have small round heads, like buttons, others like ferrets, to take the pieces out, and others flat, etc. When the stone has been engraved it is polished on wheels of hair-brushes and tripoli.
Cleaning And Preservation Of Engravings.
In commencing to restore an engraving, some attention must be given to the kind of injury it has suffered. A general brown color more or less deep, resulting from atmospheric action only, is the least possible change. Spots and stains, caused by ink, colored fluids, oil or insects, must be first treated, and all pencil marks removed by Indiarubber or bread-crumbs. A fluid acid, obtained by dissolving 1 oz. of crystals of oxalic acid in 1/4 pt. of warm water, may be used for application to all stains, and the paper should be wet with it thoroughly where spots of any kind exist.
Excepting in a few cases, this acid will not cause the removal of stains immediately, but generally it combines with the bases of them, and they are removed by subsequent steps, the thorough wetting should be done a few hours before proceeding to clean the engraving. The engraving should be placed in a shallow tub or other vessel, and allowed to rest upon a piece of open cotton stuff, or millinet. This material of suitable dimensions, should have 2 rods or sticks sewn to opposite edges. These sticks will hang over the sides of the vessel, and permit the prints to be withdrawn or moved without any risk of injury, and they should remain in soak with warm or cold water for 12 or 24 hours. When the prints no longer discolor the water on being agitated, the fluid should be withdrawn, and enough clean water added to cover them. Half a pound of chloride of lime should be made into a paste with cold water, and stirred up with 2 qts. of water, and allowed to settle for 6 hours. Part of the clear solution should be added to the bath till the smell of chlorine is perceived, and the prints should be moved to facilitate the action. In very bad cases, 1 oz. of muriatic acid mixed with a pint of water may be added, and when the bleaching is effected the prints should be well washed with fresh water and slowly dried On the first trial of this process, remarks Dr. Hayes, a degree of alarm will be felt in the case of a highly prized favorite at this seeming careless treatment; but it must be borne in mind that paper is a firmly felted mass of short fibres which may be soaked in various fluids for weeks, and resist all diluted acids and most chemical agents for a long time wet, if not exposed to mechanical abrasion by touch or rapid motion.