PHOTOGRAPHIC NOTES AND QUERIES.
Economical Way of Iodizing Paper.—The extravagant price of the salt called iodide of potassium has led me to experiments as to whether paper could not be iodized in another form; and having been successful, I offer the process to the readers of "N. & Q." Having verified it three times, I can safely say that it is quite as effectual as using the above salt.
The first solution to be made, is a saturated solution of iodine. Put about sixty grains of iodine (the quantity is not of importance) into an ounce bottle, and add proof spirits of wine; set it near the fire "on the hob;" and when it is nearly boiling, agitate, and it will soon become a concentrated essence: take now a bottle of clear glass, called a quart bottle, and put in it about two ounces of what is called carbonate of potash (nothing more than purified pearlash); fill up with water to within an inch of the neck, and agitate; when it is dissolved, add any of the other approved sensitives, in discretionable doses, such as fluoride or bromide of potassa, ammoniac salt, or common salt—it may have about sixty grains of the latter; and when all are dissolved, add the iodine. This is added by degrees, and shaken; and when it is a pale yellow, it may be considered to be ready for iodizing: from some experiments, I am led to believe that a greater quantity of iodine may, if necessary, be added, only the colour should not be dark. And should the operator reach this point, a few drops of solution of cyanide of potassium may be added, until the pale colour returns. Bromine water I believe may be added, but that I have not used hitherto, and therefore cannot answer for its effects. The paper then having its usual wash of nitrate of silver, is then floated on the solution about one minute, and the accustomed process gone through as described by most photographers. It is only disposed to require a pretty strong solution of silver, say thirty grains to the ounce of water. This I attribute to the potash being in a little more caustic condition than when recrystallised with iodine. And the only difference in the above formula between the two states is, that the iodine in the medical preparation is incorporated by means of iron filings with the water, which I only interpret into being a cheaper method; which makes its high price the more scandalous, and I hope this method will save photographers from the imposition: the price of a quart of iodide of potassium would be about six shillings, by the above about ten-pence. And I can safely say, it is quite as effectual: theoretically, it appears to be better, because iodine is exceedingly difficult to preserve after being dissolved and recrystallised. And much of it is lost in the preparing iodized paper: as, for instance, the usual way generally requires floating on free iodine at the last; and with the formula here given, after using once, some small quantity of tincture of iodine should be added before putting away, as the silver laid upon the surface of the paper absorbs more of the iodine than the potash. Therefore, a very pale yellow may be its usual test for efficiency, and the equivalent will be maintained.
N.B.—Potash varying much in its alkaline property, some samples will remain colourless with addition of iodine; in which case the judgment must guide as to the quantity of iodine. It should not exceed the ounce of tincture: about two drachms may be added after using it for paper.
Weld Taylor.
7. Conduit Street West.
Queries on Sir W. Newton's Process.—The process of Sir W. Newton is nearly similar to one I have successfully used for some years, and I can recommend it as effective and simple.
A difficulty I have lately found, has been with my iodized paper, which, when freshly used, is well enough; but if kept a month or two, will only allow of the paper being prepared to take views just before using. I should much like to know how this occurs.
If Sir W. Newton would answer the following Queries, he would add to the obligations that many others besides myself are under to him:
1. What paper does he use for positives, and what for negatives?
2. Is it not better to dissolve the silver and iodide of potassium in three ounces of water each instead of one (see "N. & Q.," Vol. vii., pp. 151. 277.)?
3. Is spring water fit for washing the iodized paper; if it contains either sulphate or bicarbonate of lime or muriate of soda?
4. How long ought the iodized paper to keep good?
5. How long should the negative paper (on a moderately warm day) keep after being made sensitive, before exposing to the action of light; and how soon after that should it be developed?
John Stewart.
Brighton.
Suggestion to Photographers.—The Rev. Charles Forster, in his One Primeval Language (p. 96.), speaks of the desirableness of obtaining copies of two great inscriptions in the Djebel Mokatteb,—one in forty-one, the other in sixty-seven lines, supposed to have been written by the Israelites during their exode. In the words, however, of the Comte d'Antraigues, which he quotes in p. 84: "Il faudroit six mois d'un travail opiniâtre, pour dessiner la totalité de ces caractères." Is not this a temptation to some of your photographic friends, who may be turning their steps to the East during the ensuing season, to possess themselves of a treasure which by the application of their art they might acquire almost in as many minutes?
Verbum sat.