العوامل المؤثرة في تقدير مدة الإظهار .. كتاب التحميض والطبع والتكبير

Factors affecting estimation of exposure time

Estimating the period of exposure depends on many factors, which we can summarize as follows:

1- Moving the sensitive layer:
The display process is activated if the sensitive layer is stirred in the presenting solution, as is the case with any chemical process that is activated by increasing stirring, and the display temperature rises slightly so the display is activated. On the other hand, the exhausted-looking solution leaves its place around the film to be replaced by another more active solution. Therefore, showing films in large tanks (shown in Figure 17, p. The two types that amateurs usually use. The reason for this is that the films do not receive continuous movement in the case of showing in the large tank, unlike showing in the first two types or showing in the Dish basin.

2- Film type and sensitivity:
A particular film may require four minutes to be shown, and another film may require five minutes to be shown under the same conditions in which the first film was shown.

3- The degree of contrast required:

The degree of variance depends to a large extent on the duration of displaying the flag, so the variance is low if the duration of display is less than the appropriate limit. The contrast becomes medium if the duration of display is appropriate, and the contrast increases if the duration of display is slightly more than the appropriate limit, then the contrast decreases if the duration of display is very long.

4- Degree of Concentration:
The display time increases when the dilute solution is used, while it decreases if the solution is concentrated.

E- The difference in the composition of the highlighting solution:
By increasing the proportions of some of the salts that make up the appearance solution, the time required for appearance is prolonged or decreased according to the quantity and properties of each salt. The research laboratories in the film-producing factories have estimated the time required for the display process with respect to each type of film they produce when displaying it in a specific solution of the display solutions that they decide.

6- Exhaustion of the display solution:

The greater the use of the revealing solution, the more its effect will gradually weaken in the process of manifesting, after which a prince said it at night specifying what calls for changing it, or adding solutions to renew its activity Replenishers | Prolonging the time required for display (and we have already talked about this subject in detail).

7- The effect of temperature on the display process:
The process of manifesting is subject to the laws of chemical interaction, one of which determines that a rise in temperature activates chemical reactions, which calls for reducing the time required for manifesting. Conversely, the time required to appear increases if the temperature decreases. May God be pleased with him, and perhaps the most suitable temperature in which the display process can be carried out is the one that ranges between (18 C - 20 C).

The following is a statement of the effect of different temperatures when showing sensitive films:
The release process does not take place where the effect of hydroquinone stops) is the most appropriate temperature to obtain the best results and the release process is in a suitable activity. It is the highest degree in which the film can be shown safely without fear of damage to the gelatin. The display process is inactive.

The film begins to bulge or swell, and it becomes dangerous to touch it, otherwise it will be removed from the abutment.
The gelatinous layer of the sensitive layer dissolves, and the film becomes worthless.

Although the aforementioned data applies in most cases, it has now become possible to display films at transfer temperatures much more than 10 °C, or even less than zero degrees Celsius, and it is also possible to find special means and solutions to increase the hardness of gelatin, and to display films at temperatures very high (about m). In view of the importance of this topic and its ramifications, another place in this book will be devoted to it to explain the methods of “showing films at both high and very low temperatures.”

The research laboratories in the film-producing factories have issued brochures showing the composition of the bleaching solutions that are suitable for the films they produce. In these brochures, the required brazing time is indicated when the temperature is between 18 C and 20 C. We show on the next page an approximate table showing the time required for braising if The temperature is higher or lower than 18°C. In order to use this table, we must first know the specific display period if the temperature of the display is 18 degrees Celsius, then we measure the temperature of the solution being used, then we extract from this table the appropriate display period for the solution temperature.