The Intensifier. We now have the four prime solutions or mixtures with which to make negatives; but as variations in light, temperature, atmosphere, and subject cause the chemicals to vary in their action, we must provide us with a further mixture to meet emergencies. This we call the intensifier. If, from over-exposure or any other cause, there is insufficient contrast between the lights and shades, the printing quality
142. This matter of the principle on which the fixing capacity of the hyposulphite depends is one that is scarcely as generally understood as it should be. Be this as it may, its importance would justify any amount of repetition. Photographers are perhaps too often disposed to think that, from a given quantity of hypo., they have a right to exact a given amount of work, no matter when they happen to be ready to require its performance, forgetting that a fixing bath begins to change from the first moment of its use, and continues to do so until gradually its silver is finally precipitated as black sulphide of silver. - M. Carey Lea.
143. When a negative properly exposed is developed, and all the details are properly rendered, we have a picture in which there is a complete scale of light and shade. That it is too feeble to print does not affect this principle. But, as soon as we begin to intensify this, we increase the amount of the lights, leaving the darks of the picture unaltered. We thus entirely alter the scale of light and shade, and often make what would have been a quiet, harmonious negative, a harsh and discordant one. One of our great defects is that we treat all faces and subjects alike. If the face is finely moulded and will bear being brought into high relief, we can well bring it up into strong light; but it would often be better to keep it in low half-tint. This is now being done much more frequently than heretofore, and we can only hope that the practice may be extended to our ordinary work. - J. C. Leake.
I do not, as a general thing, believe in intensification, but we all get caught up sometimes, and are compelled to resort to it. Take a saturated solution of bichloride of mercury, add to it a saturated solution of iodide of potassium until all the iodide of mercury is taken up, and the solution is clear again; use two or three drops of this in one ounce of water for intensifying. Should a negative become too intense, it may be reduced again by a weak solution of cyanide. No abrupt chalky lights result from the use of this intensifier, and it will bring out wondrous detail in the shadows hardly suspected before. Wash well, and do not make the negative any more intense than you desire to have it after varnishing, as the varnish will reduce it but very little. - R. Benecke.
10 to 15 ounces.
Allow it to remain a moment or two upon the plate,and then drain it back into the whence it came. From your bath - holder dip a small quantity of solution and double hulk with water. Of this add a few drops to the once need intensifier, and pour the whole over the plate again and again, until the desired int intensity is obtained. It should be the and of every photographer to obtain sufficient strength in his nega-tives without intensification, the latter being a sort manipulatory in-temperance) and an evil habit.
144. " The best method of intensification is not to intensify:it all." is a maxim held to be true by many. The great trouble about it all is that'
144. First solution. -
Sulphate of Copper,
Bromide of Ammonium,
Second solution. -
5 to 10 grains.
Take a few grains of iodide of potassium, and dissolve in a few ounces of water; then add a solution of bichloride of mercury, which will at one form a red precipitate; add mercury (a few drops at a time) until the precipitate is all taken up, or until the solution becomes clear after a good shake. - Hugh O'Neil.
|.huret of potassium may be also used in solution as an intensifier. A friend of mine, the other day, gave me a good point (which I think worth noting) in the use of sulphuret of potassium; it was to use it hot; and it is really surprising what a wonderful printing - power can be obtained by this method when occasion requires it. - A M De Silva.
Referring to the use of pyrogallic acid for intensifying or strengthening negatives after developement with iron, I stated that I had always found that the very best class of negatives of a beautiful non-actinic color were obtained by slightly intensifying. eithe r before or it fixing, by means of pyrogallic acid in combination with acetic acid. The following formula, which I have used for many years, may always be depended upon to produce good results:
..... 10 ,,
Glacial Acetic Acid.....
..... 1 ounce.
........................... 20 ounces
The above solution should be poured over the washed plate, and then returned to the de the photographer soon learns to depend on this questionable power, and neglects to take the care with his previous manipulations that he should. Thus it tends to make the careless more careless. It should only be resorted to as a sort of a resuscitation in case of accident, and not habitually. With the hope that they will not be abused, the usual methods arc given in the notes below.
145. As portrait photography is the branch of the art now chiefly under consideration, formulae for securing much greater intensity than any of these will be deferred until further on in this work. There are veloping - cup, and, after adding a few drops of a fifteen-grain solution of pure nitrate of silver, again applied to the plate. If the latter has received the right exposure, full printing density is very quickly obtained; if, however, the plate has apparently been much under-exposed, the pyrogallic solution of the above strength will probably act too energetically on the dense parts of the negative, leaving bare glass in the shadows, and producing a hard negative with too much contrast. In order to remedy this, and obtain more detail and softness in the negative, it will be found an excellent plan to avoid forcing in the first development, and to increase the strength of the redeveloping solution by the addition of dry pyrogallic acid; the latter may be added to the extent of ten to fifteen grains to the ounce of solution. This addition has the effect of curiously changing or modifying the effect of the redeveloper, which seems to lose the power of piling up the deposit on the high-lights, and acquires the faculty of bringing out the detail in the shadows to an extraordinary extent. - B. J. Edwards.