Antoine Claudet
1853
Engraving Daguerreotype Plates

Periodical article
Archive Farms
The Patrick Montgomery Collection, Object No. 2025.362
 
Periodical article from Annals of Science, Vol 1, No 22, p. 263-264, October 15, 1853
 
MISCELLANEA.
 
ENGRAVING DAGUERREOTYPE PLATES.
 
Several plans have been suggested for accomplishing this much desired object; none however, seem so well adapted as the following, recently patented by M. Claudet, to whom the art is already much indebted. In the specification, the process is explained as follows:
 
The process is established upon the following facts, which have come to the knowledge of the inventor:

1. 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 affect the white parts, which are produced by the mercury; but this action does not continue long. Then by a treatment with 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.
2. As all metallic substances 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.
3. When a Daguerreotype picture is submitted to the effect of a boiling concentrated solution of caustic potash, before being attacked by the acid, the state of the surface is so modified that the acid cleans, or leaves, in the parts which it attacks, a great number of points, which form the grain of the engraving.
4. When the effect of the acid is not sufficient, or, in other words, if it has 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 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 action of the acid alone it is not generally bitten in deep enough.
5. 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 very thin coating of copper, by means of the electrotype process, before submitting it to the operation of printing; and when the 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 affecting the metal under it; the plate is then covered again, by the same means, and is then ready for producing a further number of impressions. This repeating 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 finishing 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 areometer of Beaume (spec. grav. 1.33).
3. A solution of nitrate of potassa, composed of 300 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 excess 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 four or five thousandths of liquid ammonia. This solution will be called ammoniacal water.
7. A weak solution of caustic potash, containing four or five thousandths of the saturated solution, which will be called alkaline water.
8. A solution composed of water 8 parts, saturated solution of potash 4 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 two capsule, 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 capsule, 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 fork 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 fixed with the hyposulphite of soda, and afterwards in distilled water.
 
First process for biting in or engraving the plate.—The following solutions must be put in the capsule in sufficient quantity, so as to entirely cover the plate.—

1. Acidulated water.
2. Alkaline water.
3. Alcoholized potash in a covered capsula.
4. Caustic potash in a covered capsula.
5. Distilled water.

 
The plate being put upon the glass holder or spoon, is plunged into 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 capsula containing alcoholized potash. This capsula is covered with a glass cover, and then heated by means of a spirit lamp, to about 144 deg. Fahrenheit. The plate must remain in the capsula 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 normal 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 normal acid must be poured in a capsula, 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 alkaline water, and agitated pretty strongly; from thence it is put in distilled water. (A.)
 
This being done, the plate is plunged into acidulated water, and moved about therein for a few seconds; it is then put in the normal 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 blowing 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 into the glass funnel, and there washed with pure water, and afterwards with distilled water. (B.)
 
Then without letting the plate dry, it is put upon the fingers of the 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 the 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 placed upon the stand, the potash is heated up to the boiling point. It is then left to cool (D.), and beginning the operation described from A to D, a second *biting* is obtained; and repeating again the operations described in A and B, a third biting is produced. The plate is 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 pure and bright. This polishing is done with cotton and a pounce (pumice stone;) afterwards, the chloride of silver, filling the black parts, is cleansed by the means described in B and C. The plate is then 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 remain 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 lamp-black.
2. An electrotype apparatus, and some solution fit 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 pounce, or any other polishing powder; a ball of cotton, or any other matter, covered 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 electro-gilding which are known. The only indispensable condition is, that the surface obtained by the precipitation…. [continues]
 
LL/131092