إظهار الصور الموجبة وتثبيتها وغسيلها وتجفيفها وتلميعها . كتاب التحميض والطبع والتكبير

Chapter Ten

Showing positives, fixing, washing, drying and polishing them

Showing positive images is distinguished from showing negative images, as the steps for the appearance of images can be traced easily, as this process is carried out in a suitable safety light that usually helps to see easily in a dark room, in contrast to negative images that must be shown in complete darkness sometimes or in a safety light that is usually It is so weak that it is not possible to follow the steps of the image appearing easily. Therefore, the photographer relies in his estimation of the duration of displaying positive images on two factors: the recommendations attached to the composition of the display solution, which determine the duration of display when using a specific solution at a certain temperature, and he also depends on following the steps of the image appearing gradually, so that he can stop showing it directly at the moment he sees it Appropriate, that is, when the degree of blackness of the image reaches the required level.

The number of types of solutions for showing positive images is less than the number of solutions suitable for showing negative images. While we find that the latter may require solutions that lead to fine particles, we find that these solutions are not necessary when showing positive images.
Also, some solutions for displaying negative images lead to discoloration of the image (such as solutions in which pyrogalol enters as a reducing agent).
There are factors that affect the color tone of positive images, as they may sometimes tend to be black, or to be black with blue, black or brown, or tend to red, etc. Among the factors that It affects the color of the image, the type of salts that make up the highlighter solution, its temperature, concentration, and the duration of the highlighter. The downsampling factor, in particular, affects the color of the image:
(a) Valmitol, hydroquinone, and amidol are reducing agents that often lead to black colors (and paraphenylenediamine diamine is rarely used for this purpose).

(b) Glycine and Chloroquinol are salts that often lead to warm tones when using some types of paper. The display instructions published by the paper-producing factory are the first reference that should be referred to.
Sensitive leaves (usually chlorobromide).

Perhaps the most common cationic solutions are those consisting of methol, hydroquinone, and sodium carbonate. As a general rule, whether for negative films or positive sensitive papers, it is always better to show the film or paper in the solution recommended by the manufacturer producing them.

Solutions for displaying cations with palmitol and hydroquinone:

Highlighter solutions (palmitol and hydroquinone) for positive images differ from solutions suitable for showing negative images, and we explain that as follows:


a) Regarding the degree of concentration:

The degree of concentration of solutions for showing positive images is greater than the degree of concentration of appropriate solutions for negative images, and the degree of concentration is much higher in the case of showing bromide paper and transparent wave images, Lantern Plates if we want dark black colors, and the degree of concentration reaches its maximum in solutions for showing chloride papers We conclude that it is possible to use some palmitol-hydroquinone display solutions prepared for positive images, to show negative images as well, provided they are diluted with water. For this reason, some highlighter solutions that fall under this category are called Universal Metol because they are suitable for multiple purposes depending on their concentration, such as (Kodak 63-63), (251).

b) For the quantities of alkali:

And since there is little fear of the sensitive gelatin layer melting or swelling in the positive images to the same degree as it is feared in the negative images, and due to the possibility of increasing this swelling caused by an increase in alkalinity, therefore there is no harm in increasing the amount of alkaline salts in the positive images solutions, as in This helps to increase the speed of display and activate it.

c) For the amount of potassium bromide:

The amount of potassium bromide affects the image, and if its quantity decreases, the color of the image tends to black tone. However, it is not possible to dispense with this salt for me or reduce its quantity a lot if we want warm colors, as it also works. Prevents Fog. Based on that, its quantity depends on the type of paper that we use on the one hand, and on the color that we want on the other hand. Perhaps this explains the reasons for the multiplicity of combinations of highlighting solutions that are issued by factories, and it is recommended that they be used with each type of sensitive paper that they produce.

And the amount of potassium bromide decreases in the solutions of showing the bromide papers and increases in the solutions of showing the contact printing papers (which are the chloride papers). And since it is possible to transfer the amount of potassium bromide from the fog, so sometimes other materials are added to the solutions to show sensitive papers that prevent the fog, and at the same time help to increase the blackness of the image color, and these materials are known as developer improvers. We talked about it on (pages 85, 86). The following are examples of the composition of solutions to show positive images: