IM 



UNDULATORY FORCER LIGHT PHOTOGRAPHY. [THB DAOUKRBBOTYPB. 



THE DAGUERREOTYPE PROCESS. 



WB shall now proceed to describe, in general terms, the 

 process which, by the use of silver plates rendered 

 sensitive by means of iodine, &c., gives similar results 

 to those to which wo have already alluded. We may, 

 however, observe, that thu mode of taking portraits, 

 <tc., has been, of late years, bxit rarely employed, for 

 the collodion process has almost entirely superseded it. 



We owe to M. Daguerre the first steps which were 

 taken to render practically useful the fact that salts of 

 silver are applicable to retain the impression of solar 

 influences. It is true that Sir Humphry Davy and Mr. 

 Wedgwood were well aware that copies of objects might 

 be obtained by the agency of light ; but those eminent 

 men never proceeded oeyoud the threshold of their dis- 

 coveries. M. Niepceand M. Daguerre, however, applied 

 themselves to the subject ; and the result has been, that 

 every part of the civilised world has become familiar 

 with the fact that light may be made a most valuable 

 servant. 



About twenty years ago, M. Daguerre discovered, that 

 plates of silver, coated with iodine, were sensitive to the 

 action of light, and that those portions so acted on, 

 might afford a surface on which distinct pictures could 

 be procured. This discovery produced a profound sen- 

 sation in scientific circles ; and the French government 

 were so impressed with the novelty and value of the 

 process, that they rewarded its discoverer in the most 

 handsome manner. Ho had voted to him a pension of 

 6,000 francs ; and France took to herself the credit of 

 having given to the world one of the most surprising of 

 discoveries. 



That portion of the world which forms our native 

 land, seems, however, to have been an exception ; for a 

 patent was taken out in this country, by which the 

 employment of Daguerre's process was limited to one 

 person and his licensees. If we compare the likenesses 

 taken in the year 1840, with those of the present day, 

 we shall certainly find that we hold the palm in every 

 respect. This fact, however, must not deter us from 

 doing justice to the valuable discoveries made by M. 

 Daguerre. 



One great objection which exists against this process 

 ia. that portraits, ifec., produced by it, can only be 

 viewed in one light, owing to the reflection from the 

 silver surface. This is a source of considerable incon- 

 venience, and, indeed, prevents any chance of repre- 

 senting some objects successfully. 



We now proceed to detail each part of the process. In 

 doing so, we shall not be so minute in our description 

 as when speaking of the collodion process, for the reasons 

 which we have already given. We may conveniently 

 consider, separately, the following particulars, in the 

 order in which we have arranged them : 



1. Cleaning the silver plate. 



'-'. I "Using it, and exposing it to bromine vapour, &c. 



3. Exposure in the camera. 



4. The mercury process. 

 6. The fixing process. 



6. The toning process. 



1. Cleaning the Silver Plate. We may here observe, 

 that various sorts of plates may be employed, providing 

 a surface of pure silver is formed thereon. Hence, 

 copper, plated with silver by the ordinary method, or 

 by electrotyping pure silver plates, or standard silver 

 electrotyped over with pure silver, may be employ. > I. 

 In either case the surface requires to he highly polished ; 

 and the directions which have been given to secure this 

 desirable result, are innumerable. We presume that a 

 perfectly level plate has been chosen, free from scratches, 

 <fec. Its surface should first be roughly cleaned from 

 oxide by dipping it into, or by rubbing it over, with a 

 very dilute nitric acid ; this removes a thin ooat of the 

 silver, but ensures, at the same time, more chance of 

 success in the process of cleaning. The plate is thru 

 to be washed in plenty of cold water, so as to remove 

 all trace of acid. This being effected, it may be polished 



by the following moans : Place the plate on a sheet of 

 clean white paper, much larger than itself, and, by 

 means of a pellet of the best cotton wool, which has 

 been previously dipped in some of the best olive oil, 

 commence rubbing the plate in a circular manner, from 

 the centre to its outside. Having done this until the 

 surface is covered with oil, dust over it some of the 

 finest tripoli, and pursue the same plan of rubbing 

 circularly, from the centre to the outside, for some 

 little time. By such means all the coarse irregularities 

 will be removed, and a tolerably level surface will be 

 obtained. 



The plan which we have adopted, after having given 

 the plate the rough polish, is to wash it carefully with 

 a mixture of equal parts of spirits of wine and liquid 

 ammonia : this has the effect of dissolving and clearing 

 away the minute portions of oil which would otherwise 

 remain in the fine lines left on the surface of the plate ; 

 which, although invisible to the naked eye, may easily 

 be detected by means of a microscope. After thus 

 having cleansed the plate, it is to be held over the flame 

 of a spirit or gas-lamp, which has the effect of driving 

 away a thin film of air which always rests on polish**! 

 surfaces, and of which we have already spoken.* 



A little clean cotton wool, made into a pellet, is then 

 to be moistened with spirits of wine. Having dipped 

 it into some of the finest tripoli powder, the plate is to 

 be rubbed with it until a dark jet-like appearance is 

 produced : a dry pellet of cotton is then to be employed, 

 to remove all trace of the powder. The hist operation is 

 that of buffing, or rubbing the plate on some velvet 

 fixed tightly over a piece of wood. This is generally 

 made, in shape and appearance, like a razor strop ; and 

 the plate is to be briskly moved, under pressure, to and 

 fro on the surface of the velvet. By these means a 

 brilliant polish is obtained ; and, practically speaking, 

 we may suppose the plate as fit for all subsequent 

 processes. 



We must here warn the tyro against carelessness in 

 respect to the cotton wool, tripoli, and buffer, each of 

 which are liable to catch small portions of dust, sand, or 

 grit. Neglect of this is sure to afford a scratched and 

 uneven surface on the plate. The smallest particle of 

 any hard substance, repeatedly rubbed on a compara- 

 tively soft body like silver, produces an infinity of fine 

 lines, and renders the plate useless. Our remarks on 

 cleanliness, in a former page, have an equ.il application 

 to the Daguerreotype process ; and, indeed, too much 

 care cannot be bestowed at each step of our progress. 



When the operator has a lathe in his possession, much 

 labour is saved by its use in the operation of polishing 

 Daguerreotype plates, because both buffer and plate 

 may readily be fitted in it. The action is much more 

 regular than that obtained by manual labour, and there 

 is less risk of producing a scratched surface through 

 over-pressure on any part. We need scarcely add, that 

 the time required for polishing the plate is also mate- 

 rially lessened. 



2. Iodising the Plate. After thus producing a clean and 

 polished surface on the plate, it must then be made 

 sensitive to tha action of light by means of the vapour 

 of iodine and bromine. In the earlier days of pho- 

 tography, iodine alone was employed ; but the addition 

 of bromine has many advantages, as we shall presently 

 see. 



The philosophical instrument-makers sell boxes ex- 

 pressly made for the iodising process. The student, 

 liowever, will succeed very well by using a square box 

 of about four inches deep, and a little longer and 

 broader than the plate. The latter should be fixed in 

 a frame so that it may be exposed with the silver face 

 downwards. The frame itself may form the lid of the 

 box. In the bottom of the box a glass tray must be 

 placed, to hold the iodine, &c. A similar box will be 

 required for the bromising process, if the operations are 

 carried on separately. Of this, however, we shall speak 

 more fully as we proceed. 



To iodise the plate, put a small portion of iodine 



See ante. p. 146. 



