Sealed 21st November, 1843.

We give the following as copied at the Patent Office in London. Many of our Daguerreotypists have enquired of us in relation to the patents on the Daguerreotype in England.

These improvements consist in rendering the Daguerreotype picture susceptible of producing, by printing, a great number of proofs or copies; thereby transforming it into a complete engraved plate.

The process is established on the following facts, which have come to the knowledge of the inventor:—

1st. A mixed acid, composed of water, nitric acid, nitrate of potassa, and common salt, in certain proportions, being poured upon a Daguerreotype picture, attacks the pure silver, forming a chloride of that metal, and does not effect the white parts, which are produced by the mercury; but this action does not continue long. Then, by a treatment with ammonia (ammonia containing already chloride of silver in solution, is preferable for this operation), the chloride of silver is dissolved, and washed off, and the metal being again in its naked state, or cleansed from the chloride, it can be attacked afresh by the same acid. This acid acts better warm than cold.

2d. As all metallic surfaces are soon covered (when exposed to the atmosphere) with greasy or resinous matters, it is necessary, in order that the action of the acid upon the pure silver should have its full effect, for the surface to be perfectly purified; this is effected by the employment of alcohol and caustic potash.

3d. When a Daguerreotype picture is submitted to the effects of a boiling concentrated solution of caustic potash, before being attacked by the acid, the state of its surface is so modified that the acid spares or leaves, in the part which it attacks, a great number of prints, which form the grain of the engraving.

4th. When the effects of the acid are not sufficient, or, in other words, it is not bitten deep enough, the effect is increased by the following process:—Ink the plate as copper-plate printers do, but with a siccative ink; when the ink is sufficiently dry, polish the white parts of the plate, and gild it by the electrotype process; then wash it with warm caustic potash, and bite it in with an acid, which will not attack the gold, but only the metal in those parts which having been protected by the ink, have not received the coating of gold. By these means the engraving is completed, as by the acid alone it is not generally bitten in deep enough.

5th. To protect the plate from the effects of wear, produced by the operation of printing, the following process is employed: The surface of the plate is covered with a thin coating of copper, by the electrotype process, before submitting it to the operation of printing; and when that pellicle or coating of copper begins to show signs of wear, it must be removed altogether, by plunging the plate in ammonia, or in a weak acid, which, by electro-chemical action, will dissolve the copper, without effecting the metal under it; the plate is then coppered again, by the same means, and is then ready for producing a further number of impressions. This re-coating operation may be repeated as many times as may be required. The following is the description of the whole process, which is divided into two parts, consisting of a preparatory and printing process.

Preparatory Engraving.—For this operation which is the most delicate, it is necessary to have—1. A saturated solution of caustic potash. 2. Pure nitric acid at 36° of the barometer of BeaumÉ (spec. grav. 1·333). 3. A solution of nitrate of potassa, composed of 100 parts of water, and 5 parts of nitrate, by weight. 4. A solution of common salt, composed of water 100 parts, and salt 10 parts by weight. 5. A weak solution of ammoniacal chloride of silver, with an access of ammonia. The ammoniacal chloride of silver must be diluted with 15 or 20 parts of pure water. In the description of the process, this solution will be called ammoniacal chloride of silver. 6. A weak solution of ammonia, containing 4 or 5 thousandths of liquid ammonia. This solution will be called ammoniacal water. 7. A weak solution of caustic potash, containing 4 or 5 thousandths of the saturated solution, which will be called alkaline water. 8. A solution composed of water 4 parts, saturated solution of potash 2 parts, alcohol 1 part, all in volume. This solution will be called alcoholized potash. 9. Acidulated water, composed of water 100 parts, and nitric acid 2 parts, in volume. Besides, it is necessary to have three capsulÆ or dishes, made of porcelain, large enough to contain the plate, and covered with an air-tight piece of ground plate glass, and two or three more capsulÆ, which do not require to be covered; two or three glass funnels, to wash the plate; and two or three glass holders, in the shape of a spoon or shovel, by which the plate is supported when put in and taken out of the solution, without touching it with the fingers.

The Daguerreotype plate is submitted to the engraving process, after having been washed in the hyposulphate of soda, and afterwards in distilled water.

First process for biting in or engraving the plate.—The following solutions must be put in the capsulÆ, in sufficient quantity, so as to entirely cover the plate:—1. Acidulated water. 2. Alkaline water. 3. Alcoholized potash, in covered capsulÆ. 4. Caustic potash, in covered capsulÆ. 5. Distilled water.

The plate being then put upon the glass holder or spoon, is plunged in the acidulated water, and agitated during a few seconds, then put into a glass funnel, and washed with distilled water. It is taken again with the glass spoon, and plunged in the capsulÆ containing alcoholized potash. This capsulÆ is covered with its glass cover, and then heated, by means of a spirit lamp, to about 140° Fahrenheit. The plate must remain in the capsulÆ half an hour, during which the solution is heated now and then, and agitated. During that time the following acid solution, which will be called nomal acid, must be prepared: it is composed as follows:—Water 600 parts, nitric acid 45 parts, solution of nitrate of potassa 12 parts, solution of common salt 45 parts. These proportions are in volume. The nomal acid must be poured in a capsulÆ, covered with its glass cover, and a sufficient quantity must be kept in the bottle.

When the plate has been immersed in the alcoholized potash during half an hour, it is taken out of the solution by means of the glass holder, and immediately plunged in the alkaline water, and agitated pretty strongly; from thence it is put in distilled water (A). This being done, the plate is plunged in the acidulated water, and moved about therein for a few seconds: it is then put into the nomal acid. When the plate has been immersed a few seconds in the acid, it is taken out by means of the glass holder, taking care to keep it as much as possible covered with the solution, and it is immediately placed horizontally upon a stand, and as much acid as the plate can hold is poured upon it from the bottle; it is then heated with a spirit lamp, but without attaining the boiling point. During this operation it is better to stir or move about the acid on the plate by pumping it, and ejecting it again, by means of a pipette or glass syringe; after two or three minutes the acid is thrown away, the plate is put in the glass funnel, and then well washed with water, and afterwards with distilled water (B).

Thus, without letting the plate dry, it is put upon the fingers of the left hand, and with the right hand some ammoniacal chloride of silver, which is moved about the surface by balancing the hand is poured upon it; the solution is renewed until the chloride, formed by the action of acid, is dissolved; the plate is then washed by pouring upon it a large quantity of ammoniacal water, and afterwards some distilled water. (C.)

Without allowing the plate to dry, it is then put in the caustic potash, and the capsula being then placed upon the stand, the potash is heated up to the boiling point; it is then left to cool (D); and beginning again the operations described from A, to D, a second biting is obtained; and by repeating again the operations described in A, and B, a third biting is produced. The plate is then dried; in this state the black parts of the plate are filled with chloride of silver.

The plate is then polished until the white parts are perfectly pure and bright. This polishing is soon done with cotton and ('ponce') (pumice stone); afterwards, the chloride of silver, filling the black parts, is cleansed by the means described in B, and C. The plate is dried, but before drying, it is well to rub the plate slightly with the finger, in order to take off from the black parts any remains of an insoluble body, which generally remains on it. The preparatory engraving is then finished, and the plate has the appearance of a very delicate acquatint engraved plate, not very deeply bitten in.

Nevertheless, if the operation has been well managed, and has been successful, it is deep enough to allow the printing of a considerable number of copies.

Note.—Sometimes, instead of treating the plate with the boiling potash in the capsula, a similar result may be obtained by placing the plate upon the stand, covering it with the solution, and heating it by means of a spirit lamp, until, by evaporation the potash becomes in a state of ignited fusion. By this means the grain is finer, but the white parts are more liable to be attacked.

Last operation of biting in: This operation requires some of the re-agents, before-named, and also,

1. A siccative ink, made of linseed oil, rendered very siccative by boiling it sufficiently with litharge; it may be thickened with calcined lampblack.

2. An electrotype apparatus, and some solutions of it to gild, and copper the plate.

Means of operating: The plate must be inked as copper-plate printers do, taking care to clean off the white parts more perfectly than usual; the plate is then to be placed in a room sufficiently warm, until the ink is well dried, which requires more or less time, according to the nature of the oil employed. The drying of the oil may be hastened by heating the plate upon the stand with the lamp, but the slow process is more perfect and certain.

When the ink is well dried, the white parts are cleaned again, by polishing the plate with cotton and ponce, or any other polishing powder; a ball of cotton, or any other matter covered over with a thin piece of caoutchouc or skin, can be used for this purpose. When polished the plate is ready to receive the electro-chemical coating of gold, which will protect the white parts.

Gilding.—The gilding is obtained by any of the various processes of electrotyping that are known. The only indispensable condition is, that the surface obtained by the precipitation must not be liable to be attacked by the weak acid; a solution answering this purpose is made of 10 parts, (by weight), of ferocganide of potassium; 1 part of chloride of gold, and 1,000 parts of water, used with a galvanic battery. During the gilding the plate must be turned in several positions, in order to regulate the metallic deposit. In some cases the gilding may be made more perfect, if the plate is covered with a thin coating of mercury before putting in the gilding solution.

When the plate is gilded, it must be heated with the boiling caustic potash, by the process already indicated for the preparatory engraving, in order to cleanse it from all the dried oil or ink, which fills the hollow. The plate is then washed and dried, and when the oil employed has been thickened with the lampblack, the surface of the plate is rubbed with crumbs of bread, in order to cleanse and take off the black remaining; then, the white parts being covered and protected by varnish not liable to be attacked, and the black parts being uncovered and clean, the plate can be bitten in by aqua-fortis, according to the ordinary process used by engravers.

This operation must be used upon the stand, and not by immersing the plate in the solution.

Before this biting in, if the preparatory engraving has not succeeded well, and the plate still wants a sufficient grain, it can be given by the various processes of aquatint engraving.

Before submitting the plate to the operation of printing, in order to insure an unlimited number of copies, it is necessary, as before stated, to protect it by a slight coating of copper, which is obtained by the electrotype process; otherwise the printing would soon wear the plate. This coating must be kept very thin, but the fineness of the engraving, and the polish of the white parts, should be destroyed. In this state the plate can be delivered to the printer.

After a certain number of impressions have been obtained, it will be perceived that the coating of copper is worn in some places; then this coating must be removed, and a fresh one applied in its place. For this purpose, the plate must be purified and cleansed by warm potash, and plunged in a weak acid, composed as follows:—Water, 600 parts; nitric acid, 50 parts; nitrous acid of engravers, 5 parts; all in volume. This acid will dissolve the coating of copper, and the plate being coppered again, by the same means as before, may be again submitted to the operation of printing; and as nothing can prevent the success of a repetition of the same operation, any number of impressions may be obtained. The coating of copper can also be removed by caustic ammonia. The Daguerreotype plate engraved by this process, may also be reproduced and multiplied by the electrotype process, the same as any other engraved plate.

The essential points of this process, which constitute the present invention, consist,—

First,—in the discovery and employment of certain properties of a mixture composed of nitric acid, nitrous acid, and hydrochloric acid, in detrimental or fixed proportions. The two last mentioned acids may be employed either in a free state, or combined with alkaline or other bases. This mixed acid has the property of biting the pure silver, which forms the black parts of the Daguerreotype picture, without attacking the white parts formed by the amalgam of mercury.

The result of the action of the biting is, to form on the black part of the picture an insoluble chloride of silver; and this chloride of silver, which, when formed, stops the action of the acid, is dissolved by the ammonia, which allows the biting to continue.

Secondly,—In the discovery of certain properties of a warm solution of caustic potash, and in the employment of the said solution, by which the mercury forming the picture is better and deeper amalgamated with the silver under it, so that many imperceptible points of the amalgam are affected in such a manner that the action has no action upon them.

Thirdly,—In the discovery and employment of a process which produces a grain favourable to the engraving, by which the biting on the plate is rendered deeper. This is effected by filling the parts engraved with a siccative ink, or any other substance, and then gilding the plate by the electrotype process: the gold is not deposited on the parts protected by the ink. When the plate is gilded, the ink is cleansed by the caustic potash, and the plate may be submitted to the effect of an acid, which does not attack the coating of gold, but bites only on the silver in the parts already engraved by the first operation.

Fourthly,—In the employment of a process by which the plate is protected from the wear of the printing operation. This is effected by covering the plate before printing, with a slight coating of copper; by the electrotype process, and when the coating begins to wear, by printing, it is removed by a weak acid or by ammonia, which dissolves the copper without effecting the silver under it. The plate is coppered again, and after another printing, the same operation is repeated, so that a considerable number of copies may be printed without injury to the engraving.

Enrolled in the Pitty Bag Office, May, 1844.