PHOTOGRAPHIC CORRESPONDENCE.
Glass Chambers for Photography.—I am desirous to construct a small glass chamber for taking portraits in, and shall be much obliged if you can assist me by giving me instructions how it should be constructed, or by directing me where I shall find clear and sufficient directions, as to dimensions, materials, and arrangements. Is it essential that it should be all of violet-coloured glass, ground at one side, as that would add a good deal to the expense? or will white glass, with thin blue gauze curtains or blinds, answer?
Probably a full answer to this inquiry, accompanied with such woodcut illustrations as would be necessary to render the description complete, and such as an artificer could work by, would confer a boon on many amateur photographers, as well as your obliged servant,
C. E. F.
[In the construction of a photographic house, we beg to inform our correspondent that it is by no means needful to use entirely violet-coloured glass, but the roof thereof exposed to the rays of the sun should be so protected; for although the light is much subdued, and the glare so painful to the eyes of the sitter is taken away, yet but few of the actinic rays are obstructed. It has been proposed to coat the interior with smalt mixed with starch, and afterwards varnished; but this does not appear to have answered. Calico, both white and coloured, has also been used, but it is certainly not so effectual or pleasant. Upon the whole, we think that the main things to attend to are, firmness in its construction, so as to avoid vibration; ample size, so as to allow not only of room for the operator, but also for the arrangements of background, &c., and the sides to open so as to allow a free circulation of air; blinds to be applied at such spots only as shall be found requisite. Adjoining, or in one corner, a small closet should be provided, admitting only yellow light, which may be effectually accomplished by means of yellow calico. A free supply of water is indispensable, which may be conveyed both to and from by means of the gutta percha tubing now in such general use. We apprehend, however, that the old proverb, "You must cut your coat according to your cloth," is most especially applicable to our querist, for not only must the house be constructed according to the advantages afforded by the locality, but the amount of expense will be very differently thought of by different persons: one will be content with any moderate arrangement which will answer the purpose, where another will be scarcely satisfied unless everything is quite of an orné character.]
Dr. Diamond's Replies.—I am sorry I have not before replied to the Queries of your correspondent W. F. E., contained in Vol. viii., p. 41.; but absence from home, together with a pressure of public duties here, has prevented me from so doing.
1st. No doubt a small portion of nitrate of potash is formed when the iodized collodion is immersed in the bath of nitrate of silver, by mutual decomposition; but it is in so small a quantity as not to deteriorate the bath.
2nd. I believe collodion will keep good much longer than is generally supposed; at the beginning of last month I obtained a tolerably good portrait of Mr. Pollock from some remains in a small bottle brought to me by Mr. Archer in September 1850; and I especially notice this fact, as it is connected with the first introduction of the use of collodion in England. Generally speaking, I do not find that it deteriorates in two or three months; the addition of a few drops of the iodizing solution will generally restore it, unless it has become rotten: this, I think, is the case when the gun cotton has not been perfectly freed from the acid. The redness which collodion assumes by age, may also be discharged by the addition of a few drops of liquor ammoniæ, but I do not think it in any way accelerates its activity of action.
3rd. "Washed ether," or, as it is sometimes called, "inhaling ether," has been deprived of the alcohol which the common ether contains, and it will not dissolve the gun cotton unless the alcohol is restored to it. I would here observe that an excess of alcohol (spirits of wine) thickens the collodion, and gives it a mucilaginous appearance, rendering it much more difficult to use by its slowness in flowing over the glass plate, as well as producing a less even surface than when nearly all ether is used. A collodion, however, with thirty-five per cent. of spirits of wine, is very quick, allowing from its less tenacious quality a more rapid action of the nitrate of silver bath.