محاليل الاظهار ذات الجهد المنخفض التي تؤدي الى حبيبات دقيقة .التحميض والطبع والتكبير

Second: Low voltage display solutions that lead to fine particles:

The small size of the particles in this type of solution is achieved by using a Low Energy Developing Agent in a weakly alkaline solution (such as sodium sanitate solution). An example of this type of reducing agent is para-phenylene-diamine or ortho-phenylene-diamine.

There are results that result from the weak effort of the previous reducing agents, which we summarize as follows:

(a) To reduce the degree of contrast, it is not in the nature of these materials to increase the contrast.
(b) The effective film speed decreases, which calls for increasing the exposure to a degree that depends on the composition of the apparent solution. It may sometimes require that the exposure be increased by three or four times. To explain this, we give the following example:

If the film sensitivity speed is 32 shinners. The light conditions necessitated estimating the exposure factors in a diaphragm aperture with a speed of: 1 second, so when using some types of these solutions for display, it is required that the exposure be increased by twice, for example, as if the diaphragm aperture was estimated at 4.5 6 with a ballet speed of a second. Or it may be necessary to increase the nursing by four times (such as 5.6 with a speed of 2 seconds) when using another skin. Thus, we find that for the sake of what we gain from the accuracy of the grains, we lose, on the other hand, the advantage of benefiting from the speed of the film's sensitivity.

As a result of this previous defect, many people refrained from using this type of exposure solutions, as according to the previous example, we find that the photographer, if used, has a speed of 32 brightening, with a exposure solution that leads to fine grains, to require that the exposure be increased by four times, while he can reach To the same result, if he used a film slower by four times (26 Schiner) while showing it in a solution of a normal appearance. As the use of slow film. Its speed is 26 shinners, which in itself is sufficient to reduce the size of the granule.) Despite the use of a usual bleaching solution, we finally find that the two results are equal.

For the aforementioned reasons, it was decided to improve the previous rendering solutions in order to overcome the problem of lack of effective speed in films, when using rendering solutions of this type. This improvement is carried out by the following means:

(A) Paraphenylene diamine or ortho-phenylene diamine is added to the agent. A second abbreviation like:

_ Glycine (as in the presenting solution - Ferrania R-31)
_ Metol (as in the Windisch-appearing solution that will be mentioned later).
Pyrocatechin

(b) An alkaline substance is added to the paraphenylenediamine salt-bearing solution. only or the carrier of this salt with another reducing agent, such as mitol.

However, if the amount of metol is increased or the degree of alkalinity is greatly increased, the solution. Emergence moves from the family of solutions leading to fine granules and enters into solutions. usual display.