Summary

Various,  Notes and Queries, Number 173, February 19…

“ Shadbolt, I may observe, to one who is in the habit of iodizing paper, a considerable amount of the passage relating to cyanide of potassa could not be misunderstood; the nitrate of silver being added to the iodide of potassa, forms at once a precipitate which it is required to take up. The old double iodide says, add iodide of potassa till it does so, and it will do so; but the cyanide of potassa does it much better, and the cyanogen is lost as the paper dries, otherwise it would take no image at all. ”
Source: Gutenberg

Various,  Notes and Queries, Number 173, February 19…

“ If you follow the instructions given in our former Numbers on the Collodion Process, you must meet with success. The deposit in negatives is often much blackened by adding an increased proportion of acetic acid to the pyrogallic solution—say two drachms to the ounce, so that the solution shall be one-fifth of acetic acid. A long exposure often weakens a negative; and, during the recent fall of snow, thirty seconds has produced an effective printing negative, whilst three minutes' exposure has given a negative picture so transparent as to be useless. ”
Source: Gutenberg

Various,  Notes and Queries, Number 173, February 19…

“ On pouring the solution over the plate, there is sometimes a difficulty experienced in causing it to flow evenly. Sometimes a little more acetic acid in the developing solution, or, if the plate has been out of the bath some time, redipping it, will prevent this; but if this does not remove it, and the resulting picture is hard and unpleasant in tone, a new bath is necessary. For positives, the resulting picture is more pleasing and delicate by using the developing agent rather weak. ”
Source: Gutenberg

Get perspective with Kwize: daily news enlightened by great literature