طريقة تحضير المحاليل ١-a .. كتاب فن التحميض والطبع والتكبير

Method for preparing solutions

In the absence of instructions attached to the chemicals, do the following: 1- Prepare 75-80% of the volume of water required for preparation, boil it (to expel the air), then let it cool down until it reaches a temperature of about 38-45 C. 2- Dissolve in this quantity the chemicals mentioned in the order they are mentioned, unless otherwise stated. We do not dissolve another powder before the first powder is completely dissolved. For example, with regard to ready-made chemicals, the contents of the bag or bottle (A), then (B), then (C), and so on, must be dissolved.

3- After dissolving all the chemicals, add lukewarm water to the solution until its volume becomes as mentioned in the composition.

4- Filter the solution by placing a filter paper in the funnel, or using a cotton swab

Suppression while pouring solutions into preservation containers e - Do not use solutions until their temperature reaches the required degree, which is usually 020°C for black and white acidification solutions and about 330°C for color solutions.

Developing Solutions:

We mentioned previously the display theory, and below we will learn some information about the composition of display solutions and the properties and vocabulary of the composition. Usually these chemicals come in the form of powder packages or concentrated solutions that are dissolved in water according to the instructions attached to the packages. As for the solutions of display and fixation of colored sensitive films and papers, this is better due to the difficulty in obtaining Some chemicals, in addition to the fact that the composition of some of these solutions is still a secret for the producing company. but regarding
For black and white sensitive films and papers, most of the solutions have a known composition. Therefore, you will mention some useful combinations whose components are easy to obtain from chemical stores or photographic stores. In general, it is preferable to use the chemicals recommended by the manufacturer of the film or paper sensitive to time and temperature that he suggests.

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Some information about the components of display chemicals:

1- Developing agents:

There are many of these materials that will focus on only three, the most important of which are hydroquinone, mitol, and glycine

A- Hydroquinone:

This is a white powder that dissolves easily in warm water. It is chemically active at temperatures above 15°C. It is an active reducing agent and quickly affects areas that have been exposed to light before it affects areas that have not been well exposed to light. As a result, we find that hydroquinone increases the amount of contrast in Image . This effect is reduced by the presence of potassium bromide salt. Increasing hydroquinone in the show solution leads to warm black (reddish) colors.

Metol:

This is a white powder that dissolves quickly in water. It is a reducing agent of medium activity as its effect on well-exposed and underexposed areas is similar. This leads to a decrease in contrast in the image and an increase in metol in the display solution leads to cold black and bluish colors. Excessive skin exposure to this substance leads to skin infections.

Glycine:

A slightly soluble salt in water, and it dissolves quickly in alkaline solutions, and this substance leads to an image with low contrast and fine grains

2- Preservative:

Such as Sod Sulphite to slow down the oxidation of show agents. This salt is found in the form of (aqueous) powder or crystals. We usually use the powder, and in the absence of it we use the crystals with doubling the quantity

An activator or alkali, such as:

A - Sod Carbonate: This substance is medium alkaline and is found in the form of powder, crystals, or monohydrated water, and we usually use the powder. In the event that it is not available, one of the two types can be used. Note the following: The others

Together with 1 gm of sodium carbonate powder = 2.7 gm of crystalline 1.2 gm of monohydrate

B - Caustic soda. Hydroxide or Caustic Soda:

This substance is highly alkaline and quickly liquefies (it absorbs water from the atmosphere and dissolves in it). Therefore, it must be kept in well-closed containers. Caution must be taken when using severe skin burns because it causes

Sod Borate or Borax:

This salt is slightly alkaline, and therefore it is used in highlighting solutions that lead to fine grains. Increasing the alkalinity of the solution increases the contrast of the image, and leads to an increase in granules, as well as reducing the exposure time. vice versa .
Anti-fog or damper:


This substance prevents the formation of chemical fog on the sensitive surface that occurs

As a result of exposure factors infringement on areas that were not exposed to light, the best material to use is potassium bromide salt, and it should not be

Increasing the amount of this salt in the solution, otherwise it will lead to a delay in the display process and a decrease in the display of the image.

It is noted that reducing the percentage of potassium bromide in the solution to less than 0.1% leads to black colors in the image, while increasing it to 0.3% leads to warm black colors.

It is also noted that methol creates a medium fog, while hydroquinone causes a high fog, and therefore it needs a larger amount of potassium bromide.

Examples of the installation of some solutions for showing films