"The battery may be either Smee's, Daniell's, or Grove's; if of either of the former, it should be of two series; if of the latter, one cup is sufficient.

"The plate on being immersed in the liquid, almost instantly takes a violet color. It should be allowed to remain from two to five minutes, according to the strength of the battery, and until it becomes nearly black. It should now be carefully washed, and afterwards heated over a spirit lamp until it takes a cherry-red color, and it is then ready for exposure in the camera. Before speaking of exposing the plate, it may be well to speak of some difficulties which the inexperienced operator may find in preparing it. If the battery is not in good order, and a sufficient current is not pa.s.sed through the solution, the plate will become coated--and apparently almost as well as when the battery is working well--but on exposure it will give a negative picture, and but little colored; while if the battery is in good order, the impression is invariably positive.

"Sometimes on heating the plate after washing, the surface is covered with spots or a.s.sumes a variegated appearance. This indicates that the solution is impure, or that the plate have not been thoroughly washed and are still contaminated with the soluble chlorides which are contained in the solution.

"From the fact that the plate if prepared with positive electricity gives a positive picture, while it prepared otherwise it gives a negative, it is evident that electricity plays an important part in this process. The same is true to some extent with the compounds formed with iodine, bromine, and fluorine.

"On heating the plate, the brown coating of chloride melts into a translucent enamel, and the heat should be withdrawn when a cherry-red color is produced. It the heat is continued longer, the plate a.s.sumes a lighter color, and becomes less sensitive; and the enamel will finally scale off. To produce a picture by the ordinary process of M.

Neipce, unaccelerated, it should be exposed for from three to five hours to sunlight in the camera, though pictures may be procured by contact, in from fifteen to thirty minutes."

MULTIPLYING DAGUERREOTYPES ON ONE PLATE.

I have produced some interesting specimens of the Daguerreotypic art, by exposing in the camera only a portion of the sensitive plate to the action of light. When on the exposed portion an image is formed, then taking the tablet into the dark room, change ends and expose the sensitive portion, and produce another image, developing as usual.

This plan is adapted for taking likenesses for lockets. Two images can be presented as sitting side by side, by covering half the plate with black paper, and exposing as before. In this manner we have been enabled to surprise persons by exhibiting their portrait on the same plate with a stranger's. Daguerreotypists must be cautious in practicing this, as it might not be agreeable to the parties whose likenesses are together, by the above process. It is impossible to produce an impression without a line being seen where the edge of the paper prevented the operation of the light.

I have recently seen a fine specimen produced by another plan, which far exceeds the above, there being no line, or any peculiarity denoting two exposures. The specimen referred to, was a gentleman represented on one plate by two full length portraits. This was produced by using a black velvet for the background. The plate was exposed sufficient time to produce one impression, and then the gentleman a.s.sumed another position, and is repeated as looking at himself. From the fact that the time required to develop black velvet being so much longer than that for producing a portrait, we are enabled to produce the above interesting results.

DEPOSIT IN GILDING.

Regarding specks from bad water, I would remark that gilding should be made only with distilled water. Thus made, it produces very little deposit, even by long keeping. It therefore preserves its original strength, and works with great uniformity.

Every grain of deposit contains at least 7-10 its weight of gold, easily discoverable by the blowpipe. Such gilding is continually deteriorating, which with good chloride and distilled water may be prevented. Distilled water should also be used for the hyposulphite.

and for cleaning plates. Any good, clear water may be afterwards used for washing off, with equally good results. I am very rarely troubled with specs, and deem this as the main reason.

With a portable still attached to a cooking stove, I obtain half a gallon of water per hour, and with very little trouble. A small tin retort or still connected with a Leibig's condenser, would not add much to the "traps" of the travelling operator, and save him many a disreputable specimen.--T. J. BAILEY.--Humphrey's Journal.

PRACTICAL HINTS ON THE DAGUERREOTYPE.

The following is from Humphrey's Journal, vol. 5, and from the pen of Dr. WM. HARRINGTON, one of the most able writers upon the subject of the Daguerreotype in this country:

THE CAUSE OF THE DIFFICULTY THAT SOMETIMES OCCURS TO PREVENT THE PRODUCTION OF A CLEAR IMPRESSION UPON A DAGUERREOTYPE PLATE.

Beyond all doubt this is traceable to dampness. Truly this is not a new thought; but where does this dampness come from? How does it originate, and where is it located? Generally it has been referred to a point entirely remote from its real location.

This dampness exists particularly upon the surface of the plate; is obviously derived immediately from the atmosphere; and is owing to a certain relative temperature of the plate with the hygrometric condition of the atmosphere.

Whenever this relation exists between the plate and atmosphere, a precipitation of moisture takes place upon the surface of the plate, which render all efforts at polishing impracticable. This interference is not confined to the buffing operation alone, but sometimes is discoverable even in the ordinary process of scouring. Every one at all experienced in this art will remember that it is not always an easy matter for him, by scouring, to bring his plate to the desired l.u.s.tre.

All his efforts become unavailing; the more he rubs, the duller the surface of his plate appears; and although he renews his cotton repeatedly, still he is obliged to content himself with an unsatisfactory finish.

This relative condition is not confined to any particular season of the year, nor to any certain thermometric temperature; but may occur in summer as well as in winter; the weather being warm or cold, wet or dry, clear or cloudy, raining or shining. Under any of these circ.u.mstances, if the relation of the plate and atmosphere be such as to invite upon the plate a precipitation of humidity from the atmosphere, the prospect of producing a clear impression is quite problematical.

It is reasonable to expect this occurrence from the fact that metal is a good radiator, and radiation reduces the temperature of a metallic body below that of the atmosphere. Consequently, if this relative condition happens, the result will be as I have stated.

Bodies may be colder than the atmosphere and yet derive no moisture from it; while at the same time the driest atmosphere is not devoid of moisture, but will part with it under certain conditions.

a.s.suming for granted that this relative condition between the plate and atmosphere, disposing the former to receive the humidity of the latter, const.i.tutes the great obstacle the operator has to contend with in producing, a clear proof upon the plate, the remedy naturally suggests itself, and is very simple. It consists in merely heating the plate above the temperature of the atmosphere, previous to polishing, and retaining that temperature during the operation. Various measures might be devised to effect the desired object; one of which consists of a sheet-iron box, heated from the inside by a spirit-lamp, upon the top of which are to be kept the plates ready to undergo the process of being polished; the blocks of the swing or any other vice; or the iron bed belonging to Lewis's vice.

In cold weather, when it is necessary to keep a fire in the preparation room, all of the above may be so arranged in the vicinity of the fire as to receive the requisite degree of heat for the purpose specified.

This part of the subject, however, is left entirely for the ingenuity of the operator. No matter by hat means he accomplishes the object; all that is required is to heat the plate above the temperature of the atmosphere and retain that heat during the process of polishing.

Since the adoption of this method, in connection with my partner, T. J.

Dobyns, even in this humid climate of ours, when everything in the room is dripping with moisture, it has been attended with invariable success.

CHOICE OF PLATES, ETC.

In the great catalogue of complaints made by operators, none is more common than that alleged against the quality of plates in general use.

Although the greatest diversity of opinion exists upon this subject, nevertheless the plates of every manufactory share in this universal condemnation.

To be sure it cannot be denied but that this necessary article of utility in the photographic art has undergone a sad deterioration in quality owing to the increasing demand and great reduction in price--the plates of the present day being by no means so heavily coated with silver as formerly--but the complaint alluded to is not predicated so much upon the thinness of silver as upon a mysterious something which has conferred upon the plates the epithet of not good.

That this complaint is in a great measure groundless appears evident from the fact that while, with the same brand of plates one operator can work successfully, another encounters the greatest difficulty; while one is able to produce beautifully clear and altogether satisfactory results, the other labors under the troublesome annoyance of innumerable specks, large dark insensitive patches and brown map-like portions, together with divers other blemishes, sufficient to prevent him from obtaining anything like a tolerable impression.

From this wide difference in the results of the two operators using identically the same article, it is but reasonable to conclude that the complaint is founded in error; while the inference is no more than just, that the fault may be traced to a want of practical skill on the part of the complaining operator himself; rather than to the inferior quality of the plates.

The question, then, whether the plates are unfit for use, or whether those who p.r.o.nounce them so understand how to use them, appears to be satisfactorily answered. It therefore becomes a matter worthy of investigation, to ascertain what superior judgment and skill one operator possesses over another which enable him to work successfully a quality of plate, p.r.o.nounced by the other entirely useless.

Suppose we make a critical examination of one of the repudiated plates.

From its external appearance we have little hesitation in p.r.o.nouncing it to be French; indeed, this presumption is strongly corroborated by the fact that it is ornamented upon one of its corners with a brand to designate the manufactory from which it emanated.

Upon close inspection we cannot fail to notice a striking peculiarity upon the surface; the roughness is very remarkable; the planishing hammer has left amazingly visible indications of its busy work. One would suppose the manufacturer intended the surface of the plate to represent the undulations of the sea, instead of that smooth and level character so strongly recommended by M. Daguerre.

Such a plate necessarily requires at the hand of the operator considerable labor before the surface is in a proper condition to receive a suitable polish from the buffer. The least reflection in the world should teach any one that so long as the undulatory character continues upon the surface of the plate, it is in a very imperfect condition for buffing, because the buffer cannot touch every point equally; the elevated portions alone receiving a high degree of polish while the depressed portion, from their roughness acting as nuclei, gather dust, rouge, and other foreign bodies, so detrimental to sensitiveness. The secret of the superior judgment and skill of one operator over another, is intimately connected with this point: his success depends very much upon the first process of cleaning the plate.

Let us examine the manipulation of the complaining operator. He takes one of these plates and gives it a careful scouring with rotten-stone and alcohol or any other liquid preferred for this part of the operation--that is, he gives it what he terms a careful scouring--very gently indeed because, from the frequent trials he is in the habit of making in the camera, he fears he will rub the silver entirely away before he succeeds in obtaining a good impression. The dark patches, specks, and granular appearance resulting entirely from the unevenness of the surface of the plate, look like copper to him, and he is surprised that he should have rubbed away the silver so soon, particularly by such delicate handling.

The judgment and experience of the successful operator, however, teach him that scouring injures a plate less than buffing. He knows that unless the hammer marks be obliterated, he cannot by the buffer produce a surface of uniform polish and sensitiveness, without which a fair proof is extremely doubtful; he knows that the time employed in the preliminary operation of cleaning the plate properly is economy.

There is a style of French plates in the market, denominated heavy, which are truly excellent, if properly managed. Much patience, however, is required to remove the marks of the hammer; but with tripoli and alcohol the surface is readily cut down, and the plate is then susceptible of a beautiful black l.u.s.tre by polishing with the buffer. The complaining operator could not succeed by his own method with one of the plates; he would encounter all manner of clouds and other unaccountable phenomena; he would imagine this plate entirely worn out before it was half cleaned, and soon fix in his own estimation the reputation of the heavy plate.

In making a choice of plates, therefore, it would appear to be a matter of perfect indifference with an experienced operator what kind he would use, except so far only as the labor required in cleaning them was to be taken into consideration.

The distinction between a scale plate, a Scovill No. 1, S. F., heavy A, star, crescent, eagle, or any other brand, consists in the superior finish of some, and the thinness of the silver in the cheaper qualities.

Consequently, let the complaining operator but employ the diligence inculcated in this article, to clean his plate thoroughly, so as to bring it to a perfectly even and level surface, and he will seldom be troubled with specks, clouds, dark patches, and the host of other obstacles which heretofore have tormented him.

CHAPTER VI.

AN ACCOUNT OF WOLCOTT AND JOHNSON'S EARLY EXPERIMENTS, IN THE DAGUERREOTYPE. BY JOHN JOHNSON.