Balliolensis. We are flattered by the suggestion of our Correspondent, but we must leave the agitation which he suggests to abler hands.
Photographic Notes. In consequence of the number of Replies to Minor Queries waiting for insertion, we have been compelled to postpone the Rev. Mr. Sisson's description of a new Head-rest, and Sir W. Newton's explanation of his Process.
A. S. K. (Worthing) is informed that it is quite useless to extract the size from the paper of positive pictures, to ensure their permanence. If the hyposulphite of soda is entirely freed from them, they will bear any exposure to atmospheric influence without change. Although in all works on Photography it is recommended that the size should be extracted from negatives before waxing them, it is a process we have entirely dispensed with: if the iron is used sufficiently hot, the wax will perfectly permeate the entire texture of the paper. Our Correspondent is referred to our back Numbers for an account of the mode of taking a positive picture on glass from a glass negative.
R. S. C. (Solihull) shall receive a private communication on the subject of the construction of his glass house for Photographic purposes. There are points in it which are not generally attended to, and upon which the want of success of many operators has no doubt depended.
Tyro (March 14th). The second sample of collodion which you have used is over-iodized. It is quite requisite that it should be known that the sensitive properties of collodion are not increased by adding too much of the iodizing solution. If the collodion is good, the film is semi-transparent, of a bluish opal-like appearance. If the iodine is in excess, it becomes more opaque and creamy after immersion in the bath, and of a deep orange when looked through; whereas it should appear of a pale amber colour.
Tyro (March 17th). The reticulated appearance you complain of is from using your collodion too thick, and not giving the glass the rotatory rocking motion which you should do when you drain off the excess into the bottle. Prepare two pieces of glass with collodion: in one simply drain off the excess of collodion, and in the other use the motion which has been before described, and you will perceive the difference in the evenness of the two films.
H. Henderson (Glasgow). We consider glass baths are much superior to gutta percha in every respect. Many of the unpleasant markings in collodion pictures may have their origin in the gutta percha. This is frequently adulterated, and the nitrate acts upon the extraneous substances which are added to the gutta percha, either for adulteration, to give it firmness, or an agreeable colour. A glass bath is readily made, but the minute details of the mode we cannot enter into. Our Correspondent is referred to our numerous advertising friends, as the readiest way to supply his present want in this respect. "Jefferies' Marine Glue" can be procured at all times, the cost being about sixpence per pound. One part of marine glue, and two of best red sealing-wax, form a beautiful cement for glass baths. The marine glue, when used alone, becomes detached from the glass by the nitrate solution; and, without a substance to temper it, the sealing-wax is too brittle.
X. (Manchester). When the blue spots occur of which our Correspondent complains, it is because there is at the time of operating very feeble actinic action in the light. If he were to rub one of these pictures when dry, he would find it almost entirely removable from the glass. The occasional want of brilliancy in all probability depends on the same cause. Proto-nitrate of iron, when prepared with the nitrate of baryta of commerce, instead of pure nitrate of baryta, will often have the same effect.
Now ready, in one volume, price 21s.,