The 
Daguerreian Society


During this month (October) in the year 1841, the following article 
appeared in "The American Journal of Science and Arts" (New Haven) Vol. 
16, No. 2 (October 1841;) pages 352-354:
- - - - - - - - -


ART. X.--Improvement in the Daguerreotype process of Photography; by F. 
A. P. BARNARD, Prof. of Math. and Nat. Phil. in the Univ. of Alabama.

   Messrs. Editors,--I commenced, about a year since, in connection 
with Dr. Wm. H. Harrington of this place, a series of experiments in 
photography, according to the methods of Mr. Fox Talbot and M. 
Daguerre.  Our attention was directed principally to the Daguerreotype 
process.  From the analogies known to exist between iodine and 
chlorine, we were strongly impressed with the belief that the latter 
substance might in some manner be employed to render the surface of 
silver more sensitive to the action of light than it had yet been made.  
To determine the correctness of this opinion we instituted a variety of 
experiments, which, as they proved for the most part unsuccessful, it 
is unnecessary to detail.  The coating formed by the direct action of 
chlorine gas upon polished silver, was not found to possess the desired 
photogenic properties.  We were led, therefore, to seek whether by the 
decomposition of some compound of the metal, a sensitive chloride could 
not be produced.  Mr. Talbot had already done this in the preparation 
of his photogenic paper;  but as it was our desire to avail ourselves 
of the beautiful lights formed by the vapor of mercury, and as the 
prepared paper, at least so far as our experiments go, is not 
susceptible of receiving them, we endeavored to produce the 
decomposition upon the surface of the solid metal.  It occurred to us 
as a possibility that the iodide formed in the usual manner, by 
exposing a plate over the vapor of iodine, might perhaps give up its 
silver to chlorine, and thus produce the desired coating.  This 
impression was not verified in our first experiments, owing to a cause 
which will presently be noticed.  Perseverance, however, at length 
brought its reward.  By varying in every possible manner, the 
circumstances of the experiment, we succeeded in producing a surface so 
exquisitely sensitive to the action of light, that the image of an 
illuminated object was formed upon it in the camera in a space of time 
almost inappreciable.
   The following is the process by which this result is obtained.  Let 
the plate be prepared in every respect as if an impression were to be 
taken according to the method of M. Daguerre.  Let it be then exposed 
for the space of half a minute to the action of chlorine gas, diluted 
with common air to such a degree that it may be inhaled without any 
particularly unpleasant sensation.  It will then be found so extremely 
sensitive, that on being placed in a camera, with an aperture such as 
is commonly employed in taking miniature portraits, an impression will 
be produced upon it in the smallest time in which it is possible to 
remove and replace the screen.  The completion of the picture over 
mercury is effected in the usual way.
   A plate thus chlorized, on exposure to light almost immediately 
assumes a very deep violet color, nearly approaching black.  The 
mercury is not directly tarnished, and in this state the picture is 
even more beautiful than after being washed with the hyposulphite of 
soda.  But without this washing it cannot be preserved.
   M. Daguerre has announced that he is able to take images of objects 
in an instant of time.  I have not seen any statement of his method.  
Some of the artists in the Atlantic cities have been equally 
successful.  Their process is not that which I have here described.  I 
suppose that I am acquainted with the mode of preparation which they 
employ; but as it was communicated to me under an injunction of 
secrecy, before I had discovered it myself, although I had actually 
employed it unskilfully, and therefore without complete success before, 
I can say nothing of it here.  It will, without doubt, soon be made 
public, if it is not already known.  I believe, at any rate, that the 
chloride coating is more sensitive than any other which has yet been 
used.
   It appears to us that the lights produced by this process of 
preparation are much finer and smoother than those of the original 
process of M. Daguerre.  Some idea of the quickness of the camera 
operation my be formed from the statement of the fact, that a man 
walking my be represented with his foot lifted as about to take a step.
   The quantity of chlorine necessary to produce the effect is 
exceedingly minute.  In our early experiments we employed a quart 
bottle of the gas, opening it in a deep box, and leaving out the 
stopper while deliberately counting twenty.  Replacing then the 
stopper, the plate was laid for half a minute over an opening in the 
top.  After fifty experiments the gas in the bottle seemed not to have 
lost any of its original intensity of color.  We have better 
arrangements at present in preparation.
   Much care is necessary to avoid an excess of chlorine.  The 
principal cause of our early failures arose from an error of this kind.  
One may easily determine, with any apparatus, the time and quantity 
necessary, by laying a plate over the aperture and drawing it partially 
off at intervals.  The action of the gas will then be greatest, of 
course, upon the part longest exposed.  Too much care cannot be taken 
to exclude the light during the process of preparation.
   Tuscaloosa, July 1, 1841


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Posted for your enjoyment.     Gary W. Ewer     
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10-04-99 


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