Photographic process of the turn


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turn is an additional treatment at the time of the development of a photo pulling on black and white paper, giving a color dominant to the test.

The chemical process consists in replacing partially the money of the image by another compound preferably metal (more stable).

Synopsis

General

They are distinguished direct turns indirect turns: the indirect turns require a first bath of bleaching, before the turn itself.

Today, with the digital techniques, the turns are with the range of all one each one, in small "the Effects" of the software of image processing. The turns with old, it is a whole art using a delicate chemistry; it is longer but it is for a long time.

Processes

In the formulas indicated, the abbreviation "qsp" means "quantitée sufficient for".
In practice, considering the mixtures used, to start with the 3/4 of the quantity of solvent (here always of water).
Once complete dissolution, to add water to obtain the volume of liquid indicated.

Turn Sepia

Helmut Kohl Transfered Sepia
Test old sepia

This type of turn makes it possible to find the tonality of the tests sepia of first half of the XXe century.

There are papers allowing a direct pulling sepia (Ilford XP2 and Kodak Select 1) - it is enough to specify it!

On the basis of a black and white silver pulling, this process requires two successive solutions easy to find in the trade but even more amusing to prepare oneself.

Process, to describe....

Solution of bleaching Solution of sulphurization
Sodium carbonate 20 G
Potassium ferricyanide 50 G
Bromide of potassium 10-50 G
Water 1000 ml
Sulphurize sodium 50-90 G
Distilled water 1000 ml

Gold toning

This process, relatively expensive (the gold chloride...), gives a colour subtly gilded to the clear parts. Originally, this process also aimed at improving the conservation of pullings.

The choice of the proportions of solutions A and B mixed in the bath of turn makes it possible to obtain desired colouring.

Solution A Solution B
Ammonium sulphocyanide 10 G
Acid tartaric 1 G
Sodium chloride 2 G
Water 500 ml
Chloride ofhowever 1 G
Distilled water 500 ml

To carefully wash with water then to fix (fixing traditional) and to rewash.

Blue turn

This turn in only one bath makes it possible to obtain blue tonalities, dark blue with the blue-green according to the duration of the treatment and the type of paper.

Solution A Solution B
Potassium ferricyanide 2 G
Acid sulphuric 4 cm³
Cold water qsp 1 L
Citrate of ammoniacal iron 2 G
Acid sulphuric 4 cm³
Cold water qsp 1 L

It is necessary to add the acid in water (NEVER the reverse: risk projections) then to dissolve iron citrate in the solution obtained.

To mix solutions A and B in parts equal to the moment of employment (this bath is not preserved).

Turn with the colloidal money

The image is bleached with a bath of bleaching to which is added cupric chloride which will form cerargyrite during bleaching.

Cupric chloride 30 G
Acid hydrochloric 3 ml
Ammonium persulphate 10 G
Water 1 L

One washes the image then one exposes it in the light of the day. It is then reduced by one of the solutions below according to desired colouring.

Solution A Solution B Solution B
yellow with the red or brown-purple blue red-purplished
Stannous chloride 10 G
Acid hydrochloric 1 ml
Water 100 ml
Sulphatehydrazine 10 G
Water 500 ml
Nitrite of sodium 10 G
Water 500 ml

Turn with copper sulfate

This turn gives tonalities of the brown heat to the clear red according to the duration of the treatment.

Solution of bleaching Solution of turn
Potassium ferricyanide 50 G
Potassium citrate 200 G
Cold water qsp 1 L
Copper sulfate 50 G
Cold water 1 L

Turn with selenium

This turn reinforces contrast and gives a tonality purplished according to the duration of the treatment and the type of paper.

Process, to describe....

ATTENTION, the product containing of selenium are toxic: gloves and careful washing of the hands.


Precautions

To immediately throw the solutions after use by taking care to neutralize them.

 

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