Creating colours for dyeing fabrics

How to obtain new colours mixing dyes.

A very important aspect in textile technology is on the one hand giving colour to fabrics and on the other hand, to obtain the desired colour.

We saw in the article “Colour and colourings” that the efficiency of the process of dyeing of fabric in dye bath depends on the following factors:

  1. The affinity of the dye to the fabric

  2. The bath concentration

  3. The temperature

  4. The time of the process

If when it comes to dyeing bath we have different colour dyes with the same affinity, concentration, temperature and time of process, we will obtain a similar colour saturation and the difference will stem from the hue or chroma: the colour itself.

On the other hand, if we mix dyes and we maintain those aforesaid 4 conditions, the colour obtained will be predicted applying the concepts of substractive mixture seen in the article “Colour and colourings” and will only depend on the percentage of every dye in the mixture.

Let us see an example of the bath dyeing on 100% polyester fabric made in the laboratory with three synthetic dyes suitable for the dyeing of this composition (scattered dyes) and, therefore, with an affinity to the fibre very similar.

We work, in the first place with three dyes:

  • A → a similar tone to magenta

  • B → yellow

  • C → a blue tone

The concentrations of the dyeing solutions are 0,1 g dyeing / L. 100 ml of every dyeing are prepared weighing 10 mg of powdered dye and dissolving in 100 ml of distilled water.

Also binary mixtures to 50% of the dyes A, B and C are prepared :

  • Mixture AB

  • Mixture AC

  • Mixture BC

The concentration of the solutions are also of 0,1 g dye / L. 200 ml of each mixture of two dyes is prepared by weighing 10 mg of each one of them and dissolving the 20 mg in 200ml of distilled water.


THE DYEING PROCESS

6 samples (3x5 cm) of white polyester fabric are available to undergo the dyeing bath. 

All the baths are carried out at 80º C for 10 minutes. 

We proceed first with the dyes A, B and C. After the process the fabrics are extracted and are rinsed with water.


Let us see the result: 

From left to right: A, B and C

Equally we proceed with the binary mixtures obtaining the following result: 

From left to right:mixtures AB, AC y BC

According to the theory of the colours substractive mixture: 

For the mixture AB, if to the magenta ( colouring that extracts green) it is added yellow (it extracts blue) it must produce a colouring that extracts green and blue to the white light: red

For the mixture AC, if to the magenta (colouring that extracts green ) it is added blue (colouring that extracts green and red) it must produce a colouring that extracts green and red, but it will extract green to a greater extent as both colourings extract green and only one extracts red: it must produce a reddish blue chroma, or bluer magenta.

For the mixture BC, if to the yellow (it extracts blue) blue is added (it extracts red and green) it must produce a grey. Grey is the colour produced by the complementary colours. If the affinity of the colouring were extreme we would reach a black.

Let us check if the theory coincides with the experimental results:

 

 

Mixture AB                Mixture AC                 Mixture BC

Indeed, the experimental results are consistent with the theory. Obviously, the starting colours were not pure magenta, yellow and blue; on the other hand, to know the behaviour in some particular conditions, the experiment must be done for those conditions.

We can conclude that, when it comes to obtain colours that are not available, to know the theory of colour allows us to have a criterion to mix colours that are available in the suitable proportions.

Salvador J. Ros Turégano

Photograps bye Irene de Jáudenes Bernabé

Translated from Spanish into English by Edu Grao and Alicia Hergueta

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