第42章

A quantity of plates may be prepared in this way, and all the adhering oil, etc., may be removed by a clean hand, or lathe buff, after which each plate must be heated to the point necessary to burn off the remaining oil great care being required not to overheat the plate. A very slight excess of temperature will at once destroy all the polish previously obtained.

The test for ascertaining the right temperature is at hand;the adhering oil will be driven from the plate in the form of smoke when the right temperature is reached. The moment the smoke ceases to rise from the plate, the heat must he removed, and the plate quickly cooled upon a piece of iron.

A quantity of plates thus prepared may be kept on hand for any required time, and the labor of one minute, with a lathe or hand-buff with dry charcoal, or rather, prepared lampblack, will perfectly polish the surface ready for indexing, etc.

This lampblack also requires some care in preparing.

Take a small-size crucible, properly temper it by a slow fire, that it may not be cracked after which, fill it with common lampblack, cover it over with a piece of soap-stone, and again replace it in the fire. Build a good hard coal fire around it continue the heat for two or three hours, being careful not to raise the cover till the crucible be quite cold. Pulverize when using it.

It is very desirable to keep this lampblack dry and warm.

Some operators use much rouge I would recommend the above in preference;but those who feel that they cannot dispense with the use of rouge, had better try a large addition of prepared lampblack to a small one of rouge, as this latter article, unless great pains be taken in its preparation, will adhere and work itself into the body of the surface, so that it cannot be removed therefrom;and I have seen many specimens of Daguerreotype very much injured in effect from this rouge tint disseminated throughout their shaded features, at the same time that the whole general effect of such pictures is that of a want of life.

It is true that with the use of rouge a very high degree of polish may be obtained, but probably not higher than can be produced with many other substances of a less objectionable nature.

From the announcement of the discovery by Daguerre to the beginning of the year 1840, I am not aware of any attempt to lessen the time for the action of an image, or an impression, other than that of the reflecting camera invented by Mr. Wolcott. Early, however, in 1840, Mr. Wolcott was desirous to be enabled to further shorten the time for a sitting, and having some knowledge of bromine and its action, by request, Dr. Chilton prepared a small quantity; but Mr. Wolcott did not succeed very well with it, he having invariably used too much in combination with iodine to produce that sensitive coating now well known to the profession.

Professor Morse, of this city, Dr. Goddard, of Philadelphia, and others, in the years 1840 and 1841, were acquainted with the use of bromine.

N. Griffing, of this city, or myself, used with tolerable success, iodine in large excess to nitric acid and water; and, subsequently, to nitro muriatic acid (which reacted and formed a peculiar chloride of iodine);this latter combination proved to be preferable to simple iodine, at the same time somewhat more sensitive, and was used by me in this city up to the time of my leaving for London (October 1, 1840). On arriving in London, I instituted a series of experiments in the various chemical combinations, solely with the view to be enabled to obtain more speedily a portrait than it was practicable to do with any known chemicals at that date.

The high latitude, and the winter season of the year rendering but a feeble light at best, the greater the necessity for a more sensitive chemical preparation to the shortening the time for a sitting.

Near the beginning of the year 1841, I discovered and practically applied, chloride of iodine to great advantage, and, as far as memory serves me, I believe the first used in this country was some made and shipped, Messrs.

Harnden & Co., from London, to Mr. Wolcott, in New York.

About the same time, Mr. John Goddard, of London (who was associated with myself), discovered a rather valuable combination of chemicals, consisting of a mixture of iodine, bromine, iodus, and iodic acid, and a proper combination of those bodies gave an action somewhat more sensitive than chloride of iodine--but the "high lights"of the portraits would become solarized or overdone, more frequently with this combination than with the chloride of iodine.

Throughout the year 1841, I used, with great success, chloride of iodine, applied as one coating--occasionally in conjunction with Mr. Wolcott, attempting the use of iodine, bromine, and chlorine, and at times with more or less success. The difficulty of exactly combining, the three elements above mentioned, in order to produce a certainty of result with harmony of effect, was the work of many months, with great labor and study, the slightest modification requiring a long, series of practical experiments, a single change consuming, frequently, an entire day in instituting comparisons, etc., etc.

Early in the year, 1842, I discovered a combination of chemicals (now known in London as "Wolcott's Mixture," in hermetically sealed bulbs)of exceeding uniform character, very sensitive to the action of light, and specimens produced in 1842-3, with this combination, will bear comparison with the best specimens produced at this late date.

About the same time, I discovered that however much overdone a Daguerreotype might be, the means were at hand to save or redeem it.